I replaced the bracket that attaches the Mainsheet to the boom with a bracket fabricated by Ande Gilliam, Gilliam Welding, Hampton VA (757) 791-7710. They are about 40-50% longer to give your better holding in the slot. Powder coated aluminum. Andre has four or five more available for $270?, plus shipping arrangements.
The new bracket slid right into my main boom slot (SM #387). But confirm your slot measurements with Andre's dimensions. There might be some variation across models. Or your existing bracket might have twisted the slot.
My old one was developing a stress crack at the aft end. As the shape of the bracket was distorted by the crack it was not easy to remove so I just forced it forward enough for the new bracket to slide on.
