No, I haven't tried a large washer. I thought about it, but since the derailleur hanger and cable guides are already hacked off I was planning on keeping it a fixed gear conversion and I didn't know if that would be strong enough for a fixed gear. I was hoping that I could just fill in where the metal is missing with a tig weld and grind it flat, but I think the metal is pretty fatigued and I don't know what to do about that... Could I just anneal it? I don't know very much about working with metal. The sheet metal idea seems like it might be promising though. Thanks for your help. I'm going to go start filing. I was just waiting on another opinion before I started.