Well, I bought my Miniature Crown to use and DID carefully grind down the ridge on my Crown. It is hard to tell that the modification was done and now I can use my Horseman holder on it. Now I use Grafmatics, the RH12 Graflex back and the Horseman 6X9 backs. In fact I may try to put a Mamiya 4.5X6 back on it.

By the way, the same requirement applies if you wish to use a Horseman back on a Mamiya Press or Universal with the G back.