August 1, contacted Henry via their website.
August 18, received email from Henry that my "H015 Upgrade Request" is approved and that shipping carton(s) are on the way.
August 21, received the shipping cartons and labels, boxed up both rifles.
August 24, shipped back to Henry via UPS.
August 27, delivered to Henry.
September 1, received shipping notification that my Single Shots are on their way back to me.
September 4, rifles received.
All I can say is "Wow!" I just got them back so haven't shot them with ammo yet, but dry firing, the gritty creep is completely gone and they feel a couple pounds lighter. I'll have to dig out my trigger pull gauge and check them out. They are still heavy compared to a Timney or a tuned Remington, but significantly lighter than they were. So I say, if you have a Single Shot and are on the fence, send it back. I think you'll like the results!
ETA: I did pull out the trigger gauge. The .357 breaks consistently at 6#, the .44 just over 4#. I'd prefer they were both in the 4-4.5# range, but I am still very happy compared to what they were.