Well, I don't know if we did it the right way or not but here goes: we cut a piece of cardboard to fit around the prop, taped extra pieces to close the gap where the first cut was too big and then ran a pen around the prop to give a mark on the cardboard no more than about a 1/4" too big. Then we slowly trimmed it to size, transferred the shape to a fresh bit of card and verified the shape of the cutout. Then we used a couple of bits of timber, suitably padded, twisted the blades from fully fine to fully coarse, and trimmed further to give the clearance necessary in the coarse position - if you have a fixed pitch prop obviously omit this bit. Rechecked the final shape several times, asked ourselves if it looked sensible, could we make the cutout any smaller, was everything lined up and marked, then we transferred the shape to the spinner.
We cut the spinner using a cutting disc in a Dremel, and then sanded to final shape, checking as we went. We experimented with snips and thought it was a useless way to cut glassfibre - and probably not good for the snips. Repeated the process for the other blade. It looks good. and this system seemed to work well. Main thing was to proceed slowly carefully and to keep asking "DOES THIS LOOK RIGHT??". Think thrice, measure twice, think again and then cut once, as my father used to say.
Less of a task than we anticipated.
Chris
