I know that this adjustment is made by tightening the shift springs -- easily accessible below the carriage on either side. Dr. Polt shows where on his site (and in his book). But how is it actually done? There is a screw that should do the trick, but it has no slot for a screwdriver. Surely I don't need to unhook the spring, turn the screw, and reattach the spring? That would be tedious, and not easy to do.