One of the factors that has gotten me wondering is the "banana" effect when the case blows out assymetrically in a fat chamber, right above the web. Those cases usually show funny business at the neck thickness, too.
So I don't know which is better, to run on the rim diameter, or around the body above the web, and rest the neck, or spin on the tip. But as you noted, as long as the dial doesn't move much, you are all good.
I have a home-made whatchamacallit that runs off the case base and carries the neck with the bullet. I find TDC with the dial thing running somewhere on the bullet ogive, then poke the bullet in a smooth bullet diameter drilled hole, then yank this way and that. It's a pain, but like you saw, reduces those evil flyers.
I have noticed that banana cases shoot somewhat worse (maybe .3) compared to nice, straight cases. So I have culled some cases simply because they are problem children and will never be straight.
