Rear Fan Mount for Gregs X-Carriage

UPDATE! I'm pleased to see the positive attention this little part has gotten. I've added a version that has the belt clamps (for GT2 belts) built in, which has a couple small benefits. You can modify the scad to make something similar for your belts. Or I can help you out if you leave a note. (6/8/2013)

I'm using Greg Frost's excellent X-Carriage on my Prusa Mendel reprap. I was a bit frustrated, though, that I couldn't find any designs here to mount a fan behind the x-carriage. So I made th