I guess there's a reason why you cannot simply lay your cap stock
directly on the combing and trace onto the stock. Have you tried
spiling? In my work as a furniture maker and cabinet maker for boats I
have had good success with spiling very large pieces to fit very uneven
curves.

My method is to use pieces of 1/8" ply, wide enough to lay my pointer
stick on and temporarily fastened together to lay in a conveniently
close approximation of the curves in question, marked so they can be
put back together exactly the same way. My pointer stick has notches
cut on one edge so that I can easily trace it's location and just as
easily lay it back in the exact location later. I then use the pointer
stick to point off points along the curve in question.

I then take everything apart and re-assemble it back in the shop, lay
the pointer stick back in the various positions such that the end point
will lay on my patterm stock. Mark all the points, connect the dots and
ta daa I've got the curve. With a little care this method works
surprisingly well.

The trick is to have a pointer stick that is thin, about 2-3 " wide and
about 12" or so long with 3 "V" cuts on one edge. When you trace the
position of the stick on your 1/8" ply material you may not be able to
get all the "V" cuts to lay on the ply but you will likely have enough
to recreate the location. The stick can lay over previous positions and
often does, but the "V" cuts allow for easy re-location. Keep your
pencil sharp and the point up against the edge when marking your
locations and locating your points.

Let me know if you have any questions.