I have several sizes of the PVC sanding tools. I usualy make mine at least as long as a sheet of sand paper. The longer, the straighter the edge will be. One point, use a larger size PVC than the curve of the leading edge unless you are going to cut the pipe into 1/4's. If you use to small a pipe, the edges will dig into the wing as the leading edge curve is actually a series of curves. Just lay a small pipe, or comercial sanding tool on a finished edge. You want to make sure the the true leading edge hits the bottom of the tool before either the top or bottom edge contacts the wing. How do I know how to do it this way? Well I had to replace the top sheeting on my Ruperts because I cut through it sanding the leading edge.

I don't like the strap method as I always get a scalloped edge. Using the long PVC is like using a long plane on it.

Don