Whether you have flat or dished depends on whether you have the shorter or longer steering shaft. The dish distance was taken out of the length - 55.2 and 56 have longer shafts. Otherwise everything interchanges. I think you'd end up with the wheel in your chest if you used the longer shaft with the dished wheel... The opposite is also true - a flat wheel on the shorter shaft will give more room for a larger guy, so a 56 wheel in a 57 might be the reason you found what you did...
