Most likely why it is ripping is there is to much pressure on the arm when the pin is inserted. Try either widening the hole where the pin goes through with your dremel or dremeling the pin to be a little smaller. if the pin is loose or seems to want to fall out you can always glue it in place once it is in its proper position.
Yeah... that's what I figured on doing - drilling the shoulder hole just a hair larger. After looking at it more closely, it looks like the shoulder area may have shrunk a tad bit. The shoulder pins are 100% on the money, so it can't be them causing the problem.
Thanks.