TL;DR: Looks awesome, easy to understand, but handles like a brick. Would not fight in this ship again (see my personal caveat below). If you like to maneuver less and tank more, this ship may work for you.

Even with additional gyros (30!) and limiting myself to vanilla 100 m/s, I had a hard time countering undesired drift (due to no down thrusters) and spent a lot of time in fights reorienting unnecessarily to present my other facing thrusters in retrograde direction. This meant the limited turret firing arcs spent a lot of time NOT prioritized for pointing at the enemy. 8 thrusters are decent acceleration, but with the low turning time/radius, I often coasted out of firing range before I could reorient just to BEGIN decelerating. More carefully preplanning my own travel was often defeated by the AI opponent's own movement and direction changes.

The constant slow orientation meant my turrets were rarely in line to fire and spent a lot of time idle. Just being able to fire off a good broadside felt like winning the lottery. Never mind whether it actually hit. This was true even when I tried remaining entirely stationary, or when I tried limited maneuvering (well under 50 m/s) to pre-empt an enemy NPC's vector and trap it in my broadside line of fire.

Colossus is about right. Leave this ship parked and hope it draws and tanks enemy fire. it can definitely do that.

Caveat: Most of my NPC fight time is spent on the ground, in atmosphere with sub-200 ton ships, or in space with sub-1000 ton smaller ships. I reorient constantly, seeking positional and directional advantage and presenting front armor to enemy fire. So I may have been fighting with the Colossus with the wrong tactics and skill set. I greatly welcome constructive advice on how to fight in larger ships or less maneuverable ships, b/c I realized this is a skill set I do not have.

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The design language looks amazing. There's also 25 O2 H2 gens, which the terminal info panel for the H2 tanks says will be refilled from 0% to 100% in 14 hours? (EDIT: previously, I had incorrectly estimated refill time at 45 minutes, so I apologize for the math error) Interior is straightforward, easy to navigate. I couldn't find access to some internals like the gyros/batteries (for in-game future repairs, etc). Looks like I had to grind through the internal light armor blocks in the med bay? (EDIT: I missed the access door to the bottom engineering deck, the first time.)

Nice utility weld/grind ship included. :) (EDIT: it's been removed from the blueprint)

Firepower looks great at first.

8 forward large hydro means in space this ship can hit 100 m/s in about 6 seconds in space. It has adequate lift to be mostly neutral when empty in 1 g. By tilting the nose up, you can add the forward thrust as well, and the combined 8+4 forward+up thrusters can get the Colossus out of the gravity well. No guarantees if you load it down heavily with cargo though!

No top thrusters means this ship has to flip and burn to compensate for missing thrust in that direction. Not enough gyros (only 9? Did I miss a DLC and disconnect some?) for such a beast esp with no thrusters in one direction. On average, I needed 15 seconds to make a roughly 180 degree flip and burn to brake (15 seconds JUST to turn around; more time to do the actual retro burn). Even then, no top thrust means no station-keeping in that direction, and there will often be a tiny bit of drift.This turned out to be a big deficiency in small fights against MES AI large grid NPCs. Even against a static station, I had to spend extra time to reorient to damp the upward drift. See below for problems with targeting that were compounded by all this extra needed maneuvering.

I had to slap on prog blocks for Flight Assist (for easy prograde/retrograde thrust braking; make sure to create a group with the control seat and gyros called Flight Assist BEFORE adding the script, or it'll cause an exception error. Works great otherwise -- I use this all the time) and Delta Steering (to avoid rolling my mouse forever to make a turn).

Fly this with great caution if using a higher speed mod! At least, for my style of flying. 20 gyros is adequate -- typical time to flip was reduced from 15 to 10 seconds and much more precise; 30 was more maneuverable and fine for noncombat. Adding 150-300 tons of gyros isn't that big a deal on a 4000 ton vessel. I use some gyro mods that proportionally scale up weight, block size, and power (Huge gyros, and the rest of the Huge block mods), to save on PCU without being OP (but AQD Upgradeable gyros is a good one for a little OP w/o being totally cheaty). Net gameplay movement and targeting impact is the same as adding 20 individual gyros (the aggregated damage tanking makes the gyros more resilient and less ablative, in these quantities).

I think it's too much O2 for what looks like a fairly easy to operate ship for a small crew. Maybe just 2 for needs, but keep 4 total for redundancy?

Could use more O2 H2 gens perhaps, replacing some of the long conveyor chains for a partial discount (1 O2 H2 gen is 50 PCU and 2.5 tons, versus 2 conveyor junctions of total 1 ton and 20 PCU. Adding new O2 H2 gens this way would only be a net cost of +30 PCU and +1.5 tons.

Moving the current O2 H2 gens to replace conveyors could help save up to 25 tons and 250 PCU (which is pretty trivial for this size ship).

Replacing the rest of the conveyors with small cargo is a net 0 PCU cost, and 27 small cargo = 1 large cargo. Could then replace 1+ large cargo with other functional blocks (H2 tanks, refineries, weapons, whatever). Does tend to need an inventory mgmt script b/c that's a LOT of cargo containers. :P

Small cargo is a player preference. I like it b/c cargo shows up in terminal, whereas conveyors do not. This way, I can track down damaged/incomplete cargo containers using Show on HUD. (or a damage tracking script)

The ship is quite the tank. I took on a string of 5-15k PCU NPCs and the Colossus handled it all with little penetration or loss of functional blocks. I play with bigger explosions, critical reactors/jump drives; I penetrated and vaporized more than one large grid target (hitting either a reactor or a jump drive), and never suffered that catastrophic damage myself.

FYI, the MART script includes gyro-assist stabilization, which would make the railgun turret easier to aim and fire at long range camera zoom. Needs gyro on each of the azimuth and elevation rotor sections of the turret. Not a criticism, just a suggestion to get better effect from those high-value, expensive railguns.

14 assault turrets and 18 artillery turrets (and 2 missile turrets) sounds like a lot of firepower, but it's really hard to present even half of them to fire at any one time. Effectively, only about 5-15 of them can get a clear line of sight at any given time.

The Colossus comes in at guns:PCU at 64 guns (if I counted right) to ~30k PCU / 5k blocks. That's a pretty good efficiency ratio! Due to limited firing arcs and maneuverability, the ship is effectively fighting at about a ratio of 1:1000 at any given moment.

This is based on one available rule of thumb that measures guns-to-PCU ratio for combat effectiveness with 1 gun to 500 PCU being a good benchmark. MANY workshop blueprints mount 1 gun per 1000 PCU, which I and others I know consider to be inefficiently undergunned by both tonnage and PCU. Better ratios are definitely possible in combo with some aesthetic work, so don't take 500 to be a really stringent, design-limiting min-max flying brick.

I personally know it's possible to hit a 1:200 gun:PCU ratio and build 2000 PCU large grid ships with as many as 7 turrets (as many as 10-14 cannons!) or 9 fixed artillery cannons -- AND included some functional blocks (O2 H2 generator, survival kit) AND featured additional greebly armor blocks to make it not a complete flying brick.

The recessed fore dorsal/ventral positions for 4x3 (total 12) of the arty turrets are opposite of a good superfiring turret layout -- their field of fire is obstructed by the ship itself and the fore assault cannon turrets. Only 6 missile/arty/assault turrets (and the railguns) can directly fire forward. The aft dorsal/ventral 4x3 artillery turrets similarly can't fire forward very well b/c of obstructions.

The ship has to tilt up or down 20 degrees in order to allow one side of the other dorsal or ventral turrets to superfire. Note that this is under IDEAL conditions. This means at least 12 or 14 of your turrets will always unable to target to the front high or front low -- that's half your fire power idle, waiting for the ship to turn far enough to present a new side to the target.

I have to swing this thing around to align a very strong broadside shot, far off the axis of forward thrust (using only 3 lateral thrusters left/right each instead of the 8 thrusters to the rear). But again, broadsides inherently limit you to using half your available turrets at any one time UNLESS the turrets are mounted taller and in superfiring positions along the dorsal/ventral spine.

Moreover, the design is very compact, but it forces the turrets too close together so that they block each others' field of fire even more. Even just 1 block of space between each turret would greatly increase its field of fire.

Interior defense isn't much. No exterior PDC or gatlings means I assume you did not build this for PVP to defend against hydromen. If that's your intent, then no problem.

Most of my critique re: the turrets is impossible to neatly fix in the current ship -- it would be almost a completely different design build.