So It looks like they cant get the adaper knurled. Its possible, but takes specialized equipment. I've came to the conclusion that the disc rotor adapter will be the most reliable way to go. I went to the shop and a Tektro 900 extra long reach caliper fits perfectly in the hole for the rear wheel. The rim is designed to take rim brakes. It's just painted over. I'm going to have ss spokes installed at the shop for extra strength. Still waiting on the axles. Will be putting everything together after a spoke job.
Got a drill and two bench vises( one two or 4 way vice)? you can knurl yourself. Just buy a lathe knurler. Mount the adaptor in a drill, vice it up. then mount the knurler in the moving vice, and spin the adaptor, ram the knurler into the adaptor. then reposition and do it again until you have the area knurled. Or do it on a drill press.