Removing material from the top of the shell holder OR from the bottom of the sizing die, should allow the case to be pushed further into the sizing die, enough to swage the "belt" another few thousands of an inch shorter, such that the case would chamber. The neck and shoulder would have to take care of themselves on this first pass. Once the brass fits the chamber, then the next sizing wouldn't have to be so severe. One could set the shoulders back just enough for easy bolt closure and go from there. The belt's not critical to headspace, case just needs to fit in the chamber so the bolt will close.

I would probably remove metal from a designated shell holder. You can be sure I'm not going to be grinding on a Bonanza Benchrest FL sizing die!

DF