Siege servers have the blue fog bug
Not in DX7 they don't.
By the way, there was a (dense-ish) forest map on NA servers (not the ambush map but an older one) that didn't lag even on my poor laptop (2*2.2GHz, 4GB, ATI mob. 4570) maybe that size would ideal for your map. I don't know what it was called or if they still run it though.