I know this is frustrating!! BSP in t3ed is definitely evil in my oppinion? so you have looked at the handy tutorial yet? If not here is the link once more: http://www.planetunreal.com/phalanx/...torial_bsp.htm . We can't give you anymore advices than those in the tutorial... Just avoid too complex brushes or make them semisolid. Especially stairs and roofs should be made semisolid, because they decrease the amount cuts very much, though some people say that it does not.