I think Ireland2 meant turn the case (not the die) a 1/2-turn and run it up again for a repeat sizing step. That might help just from the double-tap invoked.
I would, however, use the calipers/.38 case measurement technique shown by Matt in an earlier post, to check the *relative* headspace of your resized cases. I just tried it out tonight w/ a half-dozen fired 30-06 cases as compared to an RCBS Precision Mic and the (relative) results were dead-on within a thousandth.
As I said before, "neat idea."