You're right. And they seal the same way at 0 rpm, 4 rpm, or 7500 if it's working the way it's supposed to. I'm not sold on anything. I'm simply following what your results are telling me based on how an engine actually works. I think that last part is what's being struggled with here.
Higher rpm can push the top ring off the ring land and lose seal. That's what I'm thinking is the issue. But that's a ring, ring gap, or piston problem. Not a head problem...lol. Check the gap on the top vs 2nd rings. If the top was gapped to be large because of the KB directions, and the 2nd was left at the usual ".004 per inch of bore" deal that's your problem. File the 2nd ring gap to .003" more than the top ring gap and clean the bores and it should be fine.
But I've been wrong before and I'm sure you'll figure it out.
