Would love to see your pressure data, not just max pressure reached but a plot of the pressure curve.
Replicas are great, but nobody is making a replica of the DA44.
I have seen several articles defending the use of smokeless powders in BP guns, but the best study still remains the Sherman Bell study published in Double Gun Journal a few years ago.
Using state-of-the-art pressure transducers and data collection, pressures (not brisance) were collected at various locations in a shotgun barrel for equivalent loads of smokeless and black powder loads.
The results indicated that you can develop equivalent loads the pressure vs. time(locations) values was within plus/minus about 100-psig, i.e. identical. In my opinion the smokeless vs. blackpowder arguement doesn't hold water any more.
Bell tested shotgun pressure curves with pressure transducers placed from 1" to 12" along the barrel of his test guns. The tests were conducted with several different powders against FFFg and all pressure curves were almost identical when compared to BP. Does a revolver barrel act differently than a shotgun barrel? Sure, but I don't think comparative burn rates of powders would change in different types of gun barrels. Besides, the tests compare BP to smokeless powders shot in the same gun barrel and it should be the comparative data not the gun that is of interest, plus it should be scalable.
The attached data comes from Sherman's work and certainly gave me a lot of confidence in my personal conclusions. I am confident that the skeptics will never be satisfied, but I can not find any data that supports thier positions and the pressure curve difference and even if it happens, so what? Peak pressures at 1" or 2" down the barrel should not make any difference in performance of the barrel.
All of us should be quite aware of felt recoil when shooting revolvers and the ability to sense hot loads is quite easy when one is used to a shooting a particular revolver. I can tell you that it is very easy to develop loads of fast butning smokless powders that have a large reduction in felt recoil as compared to BP. Also, the use of your chronograph adds to the confidence that you are not over-stressing the old gun. Less felt recoil, plus slower velocities should make it very difficult to blow up a gun that can easily handle full power BP loads.
Forgot one of your points - you're right about the repro 44 DA, but I was thinking about the S&W Heritage and Italian Russians and Schofields available out there. I shoot my Schofield often, but get out one of my Americans maybe once a year and do shoot them with reduced load BP. I use BP mostly for the ambiance and occasional comments from the other shooters . . . and yes hate tht clean-up!