You can use virtually anything known to man as a batten. It's purpose to to create uniform curves. So most important for it is to be consistent throughout its length. Be it a board, a strip of plywood, pvc, whatever. To me, 3/4x1 sounds very thick for a batten.

The sheer clamps, you can use 3/4 x 3/4 or 1 x 1. Your choice. Let your skills dictate. Smaller requires more precision up front, larger requires more trimming or living with a bit of exccess weight. I know my skills, and would have to chose the latter. But that's me. If you've got a plane, it's a quick job to shave down a 1 x 1 to a 1 x 3/4.