David,
Just as we need to have a bore clearance greater than recommended by modern piston makers to take account that our motors do NOT have a constant temperature, controlled component expansion operation that exists in liquid cooled motors I think the same applies to piston ring gaps, so I initially used the CP data for Nitros/turbo/supercharged and even then managed to break a top ring!
With CP pistons (forged, low expansion) I now increase the ring gaps by a further 10%, so on a CP piston, in a Comet, I use Top Ring Gap of 0.020", second ring gap 0.025" and oil ring gap of 0.018" min.
No issues with blow by, and no broken rings any more.
M