If you want to use fabric and doping to shrink body work toa tight fit, you should start contacting companies like the Aircraft Resoration Company at Duxford or the Tiger Club for advice. Velorexes have fabic covers but these are streched over turn buckles, with doping the material is actually shrunk to a tight water reistant fit by the doping, and this helps add strength because it holds the framework under tension. I do not know where you live, but you are probably not too far from a small aerodrome or flying club such as Headcorn, Kent. A visit to one of these would probably lead to good info.
