I scored an old fiberglass static recurve at a local antiques auction recently. It is a sort of marbled brown but has no markings on it whatsoever. It came without a string and I need to get one made. I'm lookingfor a B-50 dacron flemish twist. How do you figure the length? The bow is 65 1/2" tip-to-tip, no idea at all about poundage. Any help is appreciated.