[JesseK]

I love the use of U-channel, however usually U-Channel is weaker at the bends than C-channel. This would worry me on the outside rails on a high-impact carpet game. To keep the frame stiff, I would use C-channel on the inside (usually for those dimensions you can only find 3" base with 1.5" legs or a 4" base with 2" legs and both have a ~3/16" radius on the inside corners of the bend) and 2x1" or 3x1" box extrusion on the outside. It's roughly the same weight, stiffer, and much stronger on the outside. Possibly a little more expensive depending on the supplier. For a prototype this looks good!