Did some more patching and sanding the tread section. Lesson of the day .... don't work on the robot after having a beer. I decided to try to see how the wheels fit. Well I was distressed to see one of my outer support spacers was in the way of one of the wheels. My only option was to cut out the spacer, fill and sand the area it was in and then create a new spacer in the correct location. My first mistake was to use my rotozip to cut it out. I mangled it and made the filling and sanding job much worse. Worse yet ... and I really hate to admit this but I started cutting the wrong spacer !!! So that was another filling and sanding project I made for myself. Once it was all repaired and the new spacer in, I was happy again. You couldn't even tell all the repairs.
I figured out using 3/8" aluminum rod gave me enough room to thread the rod (axle) through the entire tread section and wheels easily. I was able to drill holes in the ends with my drill press for the cotter keys. I put a few aluminum wheels into the tread section and they looked great.
Around 8:00 pm a knock at the door from UPS ... The Styrene sheets arrived. Perfect timing.