Never would have thought of it. Thanks! I'll sock that away for a rainy day.
Today, the sun shines! I finished my check maker, and it came out good.
Checks push/snap on firm and level by hand with just a firm push. Then a run through the sizing die NOSE UP, like normal. And just look at the results. The check is flat and level on all of them. There's a bit of variation in height, on my homecast. But they had already been through my sizing die twice, so no resistance.
It might look like some of the checks are not symmetrical, that they're real thin on one edge. They're not. They're almost perfectly symmetrical. It's lube. The checks consistently pinch in a bit at the mouth, forming a tiny lube groove.
Seating and sizing is same as doing normal checks on bullets made for it. EZ peezy. Just had to stone the mouth of my sizing die a wee bit to smooth out the little sharp ledge.
And my press reaches TDC on this one, too. Utterly smooth. No jams.