I will leave a lot more meat on my next brass conversion.
So you did it once and after about 1k rounds the arbor (cylinder pin?) started coming off, and you plan to do it again?
I would venture to say that the damage started after the first round you shot, and got worse and worse until the danger became obvious. It didn't just hold up great until round 1k. I think I would just have to suffer with looking at a steel frame for the Kurst Konverter on a second try.
I put an R&D cylinder in my New Model Army Buffalo (buntline) for a minute and was tempted, but gave in to the logic in manufacturer warnings and put it back in the steel one.