Quick tip on VIS:
If you want to shave some time off of your VIS, and don't mind the r_speeds going up a bit, here is a tip.
For example, in my map I have lots of "rocks" scattered around. They are 7-sided polygons streached and edit in several ways. The VIS doesn't seem to like all of the angles and stuff.
To make VIS ignore them, just make it into a FUNC_WALL. Thats all. Don't set any spawnflags or target name, just bind it to a FUNC_WALL and thats it. It made vis go about 3 times faster, although my R_SPEEDS is up 40 polys.
Also, you can use FUNC_WALLS to make openings that open and shut instantly with triggers