Although theres a way to get around the limit for preplaced: simply place them block by block, saving every time and opening the mpq to get the trigger that preplaces them (because preplaced stuff is actually created by an invisible trigger) then put it in the actual trigger editor. Why is there a limit then? That limit is mostly to prevent gigantic loading time.
All this to say preplaced and placed by trigger is actually the same. Except preplacing is easier due to graphical support.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.