I have a P5K deluxe and the ocz cooler and the cooler doesn't fit with my 8800GTS either.
At first i just used the bottom slot but then realized that the bottom slot wouldn't run my card at 16x. So I too have a useless piece of alu. Fortunately I didn't break my vidcard. It was kinda dumb that the cooler had a thumbscrew on both sides. It only needs one.
Even with a new flat screw the cooler still doesn't fit with my board dimensions though.