Hi again cousinmark,
Thanks for the "respect;" I could/should have used, in retrospect, "assertions" rather than "these pontifical statements."
I believe the case can be made for the extra pressure being distributed radially to the barrel (which in 9mm is
thoroughly capable; compare the wall thickness difference b/t .45ACP barrels and those of 9mm!), and axially between the recoil spring and the exiting bullet, thus being fully "captured," not "absorbed throughout the handgun." An exception might be the pneumatically-assisted recoil absorption of Walther's CCP and its predecessors, but generally, with exception of neglectably higher contact stress on the (steel) breech face by the (brass) casing, the stress increases throughout the handgun due to stronger recoil springs transferring slightly higher loading to hands, and the marginally increased muzzle flip acceleration magnitude
prior to slide bottoming are not significant.
I suspect the wise counsel offered by your credible industry sources has been given in context (or assumption) of
not using appropriately stronger recoil springs when shooting +P or +P+ loads. The greatly-increased slide-frame impact loading associated with swapping out factory recoil springs for
lighter ones, as is seemingly widely done, represents real risk of frame damage, but this class of device carries, by design, substantially greater stress level factors of safety than most liability-risk products.
And the probability of my needing to actually use the
Punching Above Weight SD carry ammo/springs combo is about zero. Ps. 91.11
https://www.kingjamesbibleonline.org/Psalms-91-11/ emphasis
ALL.