We started an overhaul of the stone clamp. We have two purposes in mind.

 – Make it more compact.

 – Make it with 3 servos: one to spin the entire clamp 90 degrees; 

   one to clamp and hold a stone; and one to clamp and hold a 

   short stone that serves as our capstone.

See below sketch.

The top clamp is sized only to grasp a regular stone.

The bottom clamp is sized only to grasp a low-slung capstone.

And below are images of the clamp assembly.