Well, at least the DLC parts have a diameter a bit closer to SLS... The last time I built it, I used the extra large radial size tanks and four vectors on the first stage. That was for the Block 1A, though, which is actually easier with the new diameters. What I do for the comparative size scaling, normally, is base it on proportions to the cockpit I want to use - because, really, the key to the rocket working well is the cockpit size...

thank you ! I'm glad you like my collection.
A first version of the SLS "Space Launch System" and now available in the collection, I would make sure to improve this, the game would need orange texture so that I can make a nice booster

Nice Collection! I like your Orion spacecraft.
You should try building an SLS launcher for that - and more interestingly - use the configuration for the SLS that Dynetics proposed: the Pyrios configuration, using two F-1Bs on both strap-on liquid fueled boosters.
If you do that, I am definitely going add it to my "Future of Flight" collection I made. I already added your "SpaceShipTwo" which, by the way, I am really impressed with!