Optimize, optimize and did i mention optimize?
func_detail > as Raeven said, func_detail everything that isnt used to block vis and/or seal the map.
aeraportal > easy start, aeraportal all doors/windows.
hint brush > well, thats a tuffy part, experience with them and see how they help...
Underpass is a good map, a tad too rpg oriented but thats ok once in awhile
Resistance, havent played yet, looks nice and well done, but too much hallway for my taste.
As for Powerhouse, good mayhem map, unreal style of arena, old, but good receipe.
Avalon, no idea why it wasnt in...
While at it, ive never mange to get some prop (ie sawblades, hooks) to work as prop_physic_multiplayer, whatever flag i use they arent pickable with gravgun, they do works fine has prop_physic tho.
Fun map, only drawback, some ppl on our server complain about the spawn where you have to crouch to escape.No big deal for me, but little thing easy to fix.
Are those woodplank on the bridge individuals? how many brushes?
I guess you have them as func_detail?
Maybe you can "portal" the whole bridge with a tunnel like portal?