I was wondering if you could possibly make a version without the FOG effects? As cool looking as the fog effects are, they always seem to cause lag, at least for me and people I know.
I think this because I once had another map with Fog effects. But the part with the fog, was very small. Just one little patch of it. The rest of the map had Quake 3 type high res textures. Everywhere on the map was fine, but if you walked over the patch of fog, you would feel a lag spot there in that one place.