Well tonight was good and bad... mostly good. It all began smoothly enough; I installed the new piston rings with no issues (although two pistons needed some metal burrs removed from the ring grooves). After re-honing the #4 cylinder yesterday I oiled all the bores, oiled the pistons, and began reassembling.
I started with the two middle pistons, no problem. Then... piston #4... again...
I was pretty angry with myself to make the same mistake on the same cylinder with the brand new oil ring. I wasn't sure what to do, but I ended up reusing one of the original oil rings (checked to make sure it was still within spec first). Not happy at all about that, but I would rather go this route than wait another 1+ weeks for an entire new set of rings from Japan.
At the end of the day, here's where I stopped.
Next up: torquing the head down, which I wanted to wait in case anyone here has some wild objections to what I've done, or advice
After that I'll get the cam installed, valve train, and get ready to paint the motor!