I guess I have my own theories about all that stuff that the ring companies, and others might not agree with. I can only tell you my own observations...
I think the gains from going to that ring, from an .043 top, are so minimal, that it's not worth risking the ring losing it's ability to effectively seal half way through the season or sooner...
I want the engine to last a season.... even for the max effort heads up deal, I'd like the shortblock to live the whole deal..... So far I'm confident we aren't at the point of ripping the engine down every race....so far.
I've tried all kinds of rings and I've had some issues with some living in a high rpm condition. I've seen Face delamination, losing their shape, and tension all together when we start getting into drastically thin axial thickness... Sure some could say that's a sign of detonation etc... well, I think anyone really trying hard is going to lean on their junk and detonation is part of life with a spec fuel like we run.l
Something else to keep in mind. The ring package, transfers heat from the piston, to the cylinder.... The thinner the ring package the less surface area there is for heat transfer.... not only that, but now the ring has less structure/mass and will be more sensitive to that heat.
I've actualy stepped up in ring size in one max effort deal just to make the ring live all season... it still has an aggressive radial back cut, very low drag, but a bit thicker than the .043, and in a steel compound.
I'm at a point right now where I'd rather get a little life and sacrafice that 1-2 hp.
Refer to my comments on axial width on those. I had some issues with the .043 version of the gapless tops. They become so thin where they are stepped down, there is just no strength to them.... I would not run below 1/16" ring for a gapless top. That's my opinion.
In most cases going below a 1.0MM or .043" ring is not needed. I would also suggest keeping steel out of the second ring groove as well, they tend to be hard on the piston. We at Perfect Circle make a Napier in .043", 1.5MM, and 1/16". The Napier or THG as we call it is a great ring for oil control and I would suggest anyone to use these rings. The .8MM stuff is so expensive that I would look to a more common ring stack without the trick coatings.