Cam Clamps - CNC Wood Router

I'm looking to cut out an assortment of spiral cam clamps for my T-Nut style spoil-board. Being new to CNC I did a lot of research but could not find any drawings or plans out there. Just a lot of discussion and theory.

So I starting drawing up a simple design.

Attachment 446034

So the force perpendicular and arc center point moves depending where you are along the cam face. I understand only about 1/4 arc is usable.

My question, where is it best to place the center pivot/axis?
Is there a max ratio lift/rise for the camp?
Is there a simple formula based on tried and true verse all the theory?

For mine, I just drew a 3" circle, and offset the center hole 1/4".