When I had a lot of problems with my fps on a bigger, more open-spaced map, I read thorugh a lot of tutorials about hints/localhints and optimizing the map via the prtviewer.
During this reading process I came across a very old tut + old sample map, also regarding caulk hulling. You can grab it here.
Alt+4: Hide/show translucents (for hints)
Ctrl+D: Hide/show detailed brushes
Ctrl+P: Hide/show patches
Just go through the map and look at its structure and how the author used the hints and details.
That's the map from Quakin''s old caulk-hull tutorial: