I searched the forum posts and found a 2012 post where Mr. Mike Nicoletti stated that the long bolt was used in the regular frames and the short bolt was used in the featherweight frames. He further stated "The difference is a raised rim on the back of the long bolt. This rim can be ground off to use the bolt in a featherweight, as the length of the main bolt body is the same for both lengths. I think it would entirely possible to fashion a shim for the rear of a short bolt, and epoxy in place to obtain proper clearance with the stock head."