I scribed mine out on a piece of fiberglass.
lay out a center line and then your bow specs, Use a good straight edge and CLAMP it in place so it can't move.
If you scribe your lines,then you can sand right up to the line very nicely. I use my edge/belt sander to get close and then swith to a sanding block to get it right.
Other material will work,the fiberglass is very flexible and lays on the bow good.
CTT