From the Legit Reviews article here

Some people came to the show with custom made pots and others with ones that didn't quite fit properly and needed some extra finesse to get them to work properly. A couple of metal plates, a ton of insulating material and two big fat C-Clamps usually will work in pace of four bolts and nuts as you can see from the picture above. Just don't move the video card from side to side as that setup must weigh a ton. If you are wondering who uses C-Clamps for overclocking, it would be no other than Jeremiah 'MIAHALLEN' Allen, 29, who recently won Toms Hardware Guide "Overdrive" North America and World Champions (Team IRONMODS).
I WAS NOT USING THE C-CLAMPS INSTEAD OF PROPER MOUNTING HW ...I was only using them to hold the insulation in place Works quite well