Charlie: Not having a strain guage or transducer equipment to measure CUP, I can only say that this load is used by many other shooters of this caliber, was published by Alex and Kindler in SCN and his 17 book, and all 'normal' pressure indicators are nominal.
My primers are still showing a good radius on the edges, no primer flow into the firing pin hole, cases (and we're talkin' Hornet cases here....) seem to last more than 8 firings so far, the most any of them have been shot, and the pockets are still nice and snug.
These indications tell me I COULD go a bit higher in charge weight, but common sense and prudence say otherwise. It is a perfectly safe load in this Ruger single shot, and I've been shooting it now for exactly five years with right at 800 rounds downrange to date.
Keep in mind that this is the "bank vault" falling block Ruger also, tight neck chamber shooting only 20 grain bullets. This load is not straining either the tin-foil Hornet cases, or the rifle. As a sidenote, all bullets are coated with WS2, not that it makes that much difference, but still a factor to keep in mind.
I appreciate your comment about younger shooters and older rifles, and I always recommend using published data from manuals for those not so experienced, but this is a wildcat caliber, and published data is not available from any bullet makers manual. You do realize that we're talking about the 17 Ackley Hornet here, and not the 22 Hornet or 22 K-Hornet, right?