Well I decided to roll the dice on a Titanium cylinder that I saw on gunbroker. It looked real clean and came with ejector rod/yoke/crane assembly. Not just a raw cylinder. After reading the success of a few forum members, I decided I would attempt the surgery on my 642-1. I removed the screw on the right side, removed my cylinder and slid on the TI cylinder. It seems to have an almost perfect fit. Lockup seems tight. No sloppiness. I believe this transplant was a success! The weight reduction was quite noticeable. I am a bit nervous to fire it and test out function. Maybe some lower power wadcutters before stepping up to anything +p?