Pete,
Im not real familiar with the PM 570, but if it is like other Mac's of its time, it should have 5/16 bar studs? Echo also uses a 5/16 bar stud with a square shoulder, more like a rectangle which along with some epoxy seats them to the case. We have a couple of the Echo style bar studs here if you want some measurements and/or a pic to see if these might work for you let me know.