I't the game engine - it HAS limits, yanno! :-\
Ease up yer editing & use a little trick or two, like this:
CreateVehicle - remember this command
well, bob, use it in yer missions! :thumbsup:
It really simple (almost, heh)... it's mission making with restrictions.
ONLY create what is needed around yer start pos. Then, as you move forward, let triggers be activated by YOU or yer group; these triggers will then fire whatever scripts which contain whatever needs to be created on the map.
I.e.
I walk into a forest, this activates a trigger which creates a hostile group of troopers on the other side of that forest (near the spot where I am supposed to come out of the forest, hm?!)
Check the Ed.Depot for details & DL'able scrolls, matey!