The two bolts work in different ways. the larger one pinches across the width of the hole, and (due to a slit in the side) makes the hole a smaller diameter, clamping the shaft like a drill press base as previously discussed. Putting different washers behind the handle will change the point at which it tightens until I find a combination that fits.
The smaller one isnt really a clamp, it just has a threaded hole through the side, and the arm is just a bolt that goes through and presses on the side of the toolrest shaft to hold it still. So to change the point at which it tightens I need to shorten or lengthen the end of the bolt slightly.
The graduate (only on the main banjo for some reason) has a small brass fitting, like a bolt with no thread, which is pushed into the end of the clamp bolt. I intend to replicate this, then I can easily file the end of the brass part until the position of the handle is correct.