If and when I can, I use a white Dynex wheel which are very thin, at slow speed (manual on the box controller) to try to open it up a bit in the green state. I don't grind interproximals after they've been sintered. I think on those tight type of crowns, there wasn't probably too much tissue that was previously high up interproximally, so maybe whatever we can do will help, and be good enough? My mill can mill with a .3mm tool, but I haven't tried it yet interproxmially on a margin area.