button height for 39-002

How tall is the button? How tall is the arm? What is the exact measurement between the bottom of the arm and the top of the button?

Does the "5/16" include the bottom of the button protruding below the arm? In the original crank the bottom of the button is flush with the bottom of the arm and there is essentially no extra clearance in the pass through in the window frame. Can that button protrusion at the bottom of the arm be ground flush (I could do that), or will the the button then fall out of the arm?

The bottom button is practically flush with the bottom of the arm, but not flush enough for some old homes (like mine). I used a dremel to grind it down, and it worked fine (and took no more than a few minutes).