SIRs open a big can of worms - but if you are going to make a blankett assumption that XXXX displacement yields NNN hp, then an SIR to displacement arrangement a'la GTL is pretty much the only way to make it reasonably true. given the displacement/weight categorization then simply opening the intake should allow the displacement to hit a physical power limit on its own, though.

I guess it depends on how fast you want the class to be. I am speaking / thinking about STU in particular.

as for policing all of this stuff - the less you require to conform to manufacturer spec, the less you have to police. bore, stroke, cam, CR - easily verified and really the crux of the classification system as I see it. it sounds like the whole thing is being over-thaught. yeah, economics make "stock" more attractive than "open" but the tradeoff is variety of competition. fine line. I don't envy the STAC.

as for letters - I also have a letter suggesting the inclusion of non-USDM engines (along with 11ty other things) but I think I will pen a letter specifically outlining my thoughts on that issue.