| Do you have a copy of "Maximum Boost" by Corky Bell. It has a a great "plain english" explanation of the dynamic in Chapter 1, pages 2 through 5 (4 pages to cover what some Ph.D types cover in 40 pages of barely intelligible blather IMO). If you don't have it, I will scan the pages and post them a little later.
Here is a quick link to engineering modelling discussion that gets into the math a little more. It is focussed on the connecting rod, but the conclusions drawn would also apply to the wrist pin, assuming that it is the weakest link.
La-Z-Link And a handy quick reference forum for mech eng types: La-Z-Link So when I look at all of this I concur with Bell that the tensile load on the conn rods and wrist pins (when the piston is stopping and changing directions at TDC) is the one that you need to worry about, and that (within reason ie. normal operation ie. not detonation) we should worry more about significantly increasing the rev limiter than significantly increasing the boost for a given piston design (because of the rpm squared relationship). So back to the ratings, I don't see how they can simply apply an unqualified HP spec to a piston. By definition, that imbeds a bunch of assumptions (and not just about RPM if you get into it formulae deeper). Plus I suspect if the rating is based on some type of thermal limit for the rings or the piston itself you get into the same problem.
Hopefully someone can clarify how the HP ratings are established.
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