You can give it a try. Thats how my 8800 GTS is. And I did that same thing with my x1900GT.
I found those plate covers trapped the heat inside. Didn't provide near enough air flow. I took them off and slapped a case fan on it and lowered my temps by quite a bit.
My Overclocked 8800 gts idles at 53c and tops out at 63c under load.
Instead of going out and paying 50 bucks for a cooler. I took a fan out of my junk computer parts box and lowered my temps for free
I even did it with my case. Cut a hole in the side and slapped a fan in there which helped lower my temps too.
How I mounted the fans on the video card tho I used coated wire, and spots on the Heat Sink/Card where the wire would not interfere with anything, and that where sturdy enough to hold it into place when tightened.
If I plan on selling it down the road I won't end up with a chewed up heat sink fins or something from screws.