This was my solution. I got some green foam which is more dense, and so better for molds, then I made templates that were 1/8th bigger than the final size. I hot wired them then removed them and sanded down to the final templates with my long sanding board. Much easier than sanding solid basswood. My tube of Sig-ment should be here today so I can glue my balsa sheets together.
MM
When I was hand cutting foam wings I had much better results cutting with the airfoil laid flat, not standing up like your leading edge.
Try putting the template horizontal. Put a pin into the leading edge center line. Pin it onto the ends of the foam block. Put some weight ont he block such as a strip of 1/4 in. steel. Start the wire. Lay it on the pin and pull it towards yourself. Pick it up slightly as the wire hits the template and pull it around,
I found cutting the foam with a vertical movement was very difficult. It's too easy to pull the wire off the template. Nothing provides uniform pressure like GRAVITY.
Then take the excess and tape it back in place. Turn the foam block over and repeat. You might find it easier to cut more of the airfoil, say 3-4inches, for more maneuvering room. File a slight dent in the foam, top and bottom, where the cut off will be. Then stop the wire in the notch for a couple second to make a clear mark for trimming.
We cut several hundred wings this way for both combat and stunt.