I had a rare day in which I was able to get back to the Vortex. I made up the bracket which holds on the rear brake caliper. Here is a picture of the bracket,. I had to profile it a bit to fit the caliper better.

Here is the bracket welded onto the swing arm. I will need to change the bolts used to hold the pulley/rotor on the axle as the heads of the hex bolts are causing some interference with the brake caliper.

I also put the drive pulley onto the intermediate shaft so that I could get an idea if the rear adjusting slots were sufficient. It looks that the slots were made long enough, if I get a lot of streatch from the belt I can always remove the swing arm and enlongate them some more.