This is a derivative of one of the parts (shoulder_holder_160.stl) that Flummer posted that makes it compatible for printing on a thing-o-matic. Basically the original part prints the whole shoulder rest in one print, and it's just too big to print on my thing-o-matic. So I chopped it in half, filled the original holes, and put new holes in place. Instead of one hole per half, there are two, so there should be no problem with stability when the shoulder rest is clamped to the rails. This thing was made with Tinkercad. Edit it online https://tinkercad.com/things/aVRoEzQC9FaPrint two copies of this thing, and then print four of the "shoulder_holder_bracket.stl" things found here: http://www.thingiverse.com/thing:29677 ... this bracket part holds the shoulder rest to the rails.