@M. De Land, I'm in doubt that I could accidentally discharge a loaded and capped Pietta cylinder using CCC caps, given the recessed cones and the forces of strike needed to fire the caps, however even if I thought of it as a risk, I doubt that it would deter me from having one in every pocket when riding into a close combat situation, which is already pretty high risk. Carried in a fitted leather box I believe it would be as safe (or safer because of the box cover) as the capped and loaded cylinder in the gun, the only danger time might be when transferring into the frame, if dropped but on a moving horse you'd be yards away when it hit the ground.
RE the misalignment of barrel and spare cylinder, that is what brought me to this forum in the first place, searching for input on the same situation. I have a couple of notions about improving that, but was hoping for someone who has already fixed one.