EVERY BRICK IS A BOX
Actually, I have 2 sets of 16 unit sized boxes under 5 spotlights, one set is under water, and they're arranged to strain vvis and vrad. (The lightmap scale for the walls and floor are 2) They're all brushes, no func_detail. (there's 6814 portals!)
EDIT: I've been running it for a while, CPU has been at 100%.