It seems that maybe this multi grade oil we all use maybe too light for the heat? Possibly a straight weight oil might not be able to get by the head gasket. Same with my tranny leak, maybe with straight heavy gear oil it wouldn't leak.
Thought?

And maybe if H-D quit using chit for brains along with cheap Chinese parts no one would be having these issues at all.
If the design and the parts were good, even the lightest weight oil known to man would not leak. The oil viscosity, or the fact it is synthetic and not dino oil, has absolutely nothing to do with the leak issue. Trust me, you don't want to use straight 50 or 60 weight oil in a modern engine, or 140 in your trans. Good lubrication relies on proper flow at all temps, and heavy straight weight lubes don't flow worth 10 cents at low temps.
There obviously is a design and/or manufacturing issue that needs to be addressed by the MoCo. Short of rebuilding the engine yourself with better quality aftermarket parts, I don't see any other actions you could take on your own to correct the problem.
Jerry