I ultimately decided it would be easier to get the shear webs trimmed with them in position on the wing. I put the right aileron and left flap on the wing and trimmed them close with the Fein tool. I then put a piece of masking tape on the top surface of the wing to protect it from the sanding block. I then sanded the webs to the top of the wing. When I started tearing into the tape I stopped. I also final sanded the LH aileron web using this method.
Flap Shear web after sanding - note protective blue tape