just start a new game till sid sells the 5.45 groza and then sell everything in cordon to buy it, disappears forever if you leave

By doing so, you break the entire Game, also you cut out fighting szenes wich are for the later Game storry related, Garbage + the ambush fight in front the Lab. + the Duty ambush.
Sure you could just skipp them, but that wouldlead you into a Bad Guy - Bad End -- Game.
I know its hard to explain the viewers all that into one clip.
It is possible indeed, but i would not recommand it to anyone who wants to end also this Game walktrough / Not if its your very first Try.
Anyway, good work mate. Cheers.

I didn't know those mega-stashes existed

Wack