I have used the TRF 511 body without any issues on my TRF501x without any issues with the motor rubbing ... and a JConcepts Finisher body for the B44.1/2 and that had even more room... the Pro-Line Bulldog body for the TRF502x is rather narrow for the 501x so that one would not be a good idea
Now as were to get a TRF 501x WE body from.. they are very few left at most of the stores in Japan... most places in HK with have them but they are going to cost quite a bit
