Do you have a better closeup of the affected area? Are those rings intact? What does the bore look like?
Given the top ringland looks intact that rules out detonation and AFR. It doesn't look completely scuffed so it may not be overheating. That leaves it down to insufficient ring gap, improper assembly, insufficient material/design, or the toughest of all, inter-ring pressure.
It ran for 20k miles being run pretty hard in that time shifting North of 7k. But i drove 700 miles each way two years ago on a road trip. I assembled the motor myself and set all clearances for light boost because at the time that was my goal.
It's always tough to look at a couple pictures and tell, but between the look of bending on the broken ringlands rather than a clean shear, and the scoring on the bore, I'd strongly lean toward insufficient 2nd ring gap leading to ring butting and ringland failure in this case. Did you gap the rings yourself, and if so did you record the values?
I did gap them myself and record the values but I can't seem to find them right now. I know i gapped them big to accept boost. From what I've seen, it's possible that because the drivers head I have is one with the cooling issues, it caused that cylinder to overheat. maybe that caused the ring to expand too much?
I would be skeptical of overheating as a root cause. Usually if it's overheat both sides of the piston are scuffed to hell. I see a little scuffing on that one, but nothing outrageous. When they overheat it looks like someone smeared aluminum all over the bore too, and even then I've rarely seen a ringland failure with that. If cylinders 6 and 8 look pretty scuffed/melted too it might lend some credence, but short of that I'd be skeptical.