Sounds like I built my wheels much the same way that you did. For the center core i used a lightweight 1/2" foam filled pvc plastic called Sentra. I drilled the center hole first and then sawed a circle based on that center hole. After that i secured the part in a drill press using the center hole and shaped the outside diameter. A lot of work with a 1/2" round file with the wheel center in the drill press provided a nice deep groove for the tubing to set in. It took some experimentation to get the correct length on the tire which was made from automotive black tubing. Cutting the ends of this tube nice and square was a real job. After i got a nice fit then i fitted a smaller tube about 1/2" inside and put the entire tire on the center hub. Once satisfied with the fit Thin CA secured the entire unit. Sanding with fine grit paper smoothed the joint and the entire tire was sanded to complete this process. Then the raised portions of the center hub were created using balsa and the entire wheel was placed back on the drill press for shaping. Next added a small diameter nylon tube for the wheel hub bearing. had to drill the hole in the center hub just a little larger for this bearing. After that the tire was cleaned with acetone to bring back the nice black finish. Last step was to seal the balsa on the hub with dope and painted with red dope. Sounds like a lot of work and it was!<div></div><div>Hope this helps. My Bristol is now retired and hanging in my workshop as i have moved on to much larger aircraft. The Bristol was fun though.</div>