Look through the rigs thread.  I'm pretty sure someone in there has built a K'Nex rig to support his/her cards

yes those are lego...and duplo...It's a holdover until I get some time to build the wood frame.  Two 6970's at ~360MH/s on stock voltage and one 5830 at 270MH/s, also on stock voltage...all running on linuxcoin.  Using the GPU fans @ 50% they all hover around 73C in my basement drawing 720 watts.