perfect timing - i'm considering doing this as well. a couple of additional questions ...
1) how ciritical is an interior doughnut patch for a floor? i noticed this nrs video for replacing a raft valve doesn't mention it
2) i have an nrs doughnut patch and notice the diameter is wider than the i-beams in my floor. i was thinking of cutting the patch into a narrower, rounded rectangle to avoid it spanning the i-beam seams. is this a bad idea?
this site is invaluable ... i appreciate any tips or suggestions you may have!