I have a 20" frame I am currently working on which came with a 3 piece cottered crank. I have a really cool solid sprocket (thanks Dingo!) and 1-piece crank I want to get in there, but it just won't fit. Too tight! Has anyone had any luck filing down the insides of the BB shell to expand the bearing holder thingies? I think if I could just make it a bit wider in there I could get it through.