Many thanks, Neil...
Sure, over time the cuts become the same from puzzle to puzzle of the same stamp. I've probably cut almost 2000 of these one-cent stamps. I'm especially locked in because of my fairly rigid color line cutting, e.g. the bird is cut into three pieces. But there's no way I could stack cut these. The size is just too small and even the tiniest variation (1/64") would ruin at least one. Besides, the thin blades would never take it. (I break enough as it is - yesterday I broke four in a row before getting one to take the minimum tension).
I sincerely appreciate everyone's interest. That's what makes it all worthwhile. Sometime in the late summer I'll make a little video of cutting Christmas card puzzles.
Carter