Interesting read on the parallel thread.
I got a Marvel conversion when I was on a .22 binge following open heart surgery. I tried it on the 3 .45 frames I have and it really only worked on one, an old Colt Series 70. Not a problem. Now when I play with .22s, I have the choice of the Marvel, a .22 Kadet conversion on a CZ-75, a S&W Model 41, a Ruger Single Six, a S&W 617, and a couple of Ruger Bearcats.