Hi Matt an Bengt
I picked up a 2nd hand re-centering ring and S16 gate from eBay about a month ago and performed the modification myself. Installing the new ring was no problem, the gate requires more effort and care but was fairly easy following videos that can be found on the link posted by Bengt. I shot a test roll and there were no scratches (even with loop formers left on). I would however remove the loop formers if you do the modification as this will make the camera easier to load.
cheers
Antoni