Techniques for improving framerates. Layout design, structural vs detail brushes, hint brushes, & proper use of caulk texture.
I AM NOT AN EXPERT! You'll notice I could probably do a better job with the hint brushes. Trial & error is what it's all about.
You can grab the test map file HERE & try experimenting with hint brushes to see if you can get a better result. (You can!)
Video at moddb
If you want to watch in full screen, this youtube upload is higher quality.
For a more detailed explanation of the BSP process, see Spog's Technical Notes.