Help Optimizing De_drought

[Wheel-Knee]

Hey. So I built de_drought, and it seems to be fairly well recieved other than the fact that it drags fps into the dirt. I have tried to optimize it to the best of my abilities, but apparently thats not good enough. Is there anyone here that has experience optimizing large maps that can help me? Tell me what method I should use. I've done a lot of reading, but....
If someone is ambitious and would like to take a look at my .vmf that would be cool.

Should I be using hints? area portals? I just dunno.
Check out the map here:
www.pcgamemods.com/8896/

thanks
Wheel