thanks, that was the info i needed:)
too bad that they are going to be visible all at one time, but partly (if that counts)
i am building a very large city and have all houses on mdl, all streets and sidewalks one mdl, all skyscrapers one mdl. because if i use single mdls i would place them till i die

maybe i have to try another aproach. but i wanted to use baked texture and thus the placement must be 100% accurate