I've read and studied this thread from end to end. I've enjoyed it and learned a lot.
Based on ZZZ's measurements and reported replacement joint performance, when the time comes, and I expect it will in another 500 to 1,000 hours (I'm at 2,020 now on my '04), I'm going to spend the money to get the Kubota U-Joints.
In cases where the use of the RTV hasn't change one bit, the original U-joints lasted from 1,000 to 3,000 or more hours. Replacements with other than Kubota joints last a quarter to a half as long.
On Collie's '05 machine, if I understand it right, the first time the joints were replaced it was at a Kubota dealer, the dealer didn't do a particularly good job, and the new joints lasted nearly ~1,800 hours - or about as long as the factory new joints.
Others on here are doing an excellent job of workmanship with non-Kubota parts and they don't last half, or sometimes even a quarter, that long.
There's a message, at least for me, in that data. Unfortunately, if one has ground the yokes to use after market parts with a wider clip spread, there is probably no going back to stock parts.
YMMV.
Fitch