Rather than break the inside corner of the binding (a good idea, though) I use a chisel as a scraper to clean out the inside corner of the rabbet. I wear a magnifier as I go, and any small weirdness of the rabbet can be fixed with the chisel. If anything looks funny I slap in a length of plastic binding to check the fit at that particular point, looking for gaps. I only dry fit the entire wooden binding on cutaways. If the bend is close and the rabbet is clean, there is never a problem. In fact, the wooden bindings for O, OO, and OOO guitars are interchangeable, likewise with D and slope D bodies. They aren't the same, but bindings bent to any one of them fit the others. None of my ukes interchange, worse luck.