There's a wholesaler in Illinois by the name of "Advantage Wholesale." You should be able to find a dealer in Michigan that has heard of them or regularly buys from them. They usually have a good supply of the stuff that is less like carpet, and more like woven fabric. Anything with a carpet backing is a pain, and not what the "real" companies are using. As for the joint I can't say unless I saw the design. My big rack is basically a 2x4 frame with 1/8" ply just for covering. The frame is self sufficient. Since rack gear comes in from the ears, you might run a 2x4 or 2x2 up in each corner and glue-n-screw without having to dovetail it. The gear on top and bottom shouldn't hit the corner blocks.