I've completed the hydro clutch mod, I've got a couple hundred miles on it, and it is an overwhelming success.
The Super RustBucket had a pretty hard cable clutch pull. I was never able to get a very satisfactory cable routing. With the hydro clutch, the pull is now about 30% of what it was before. Maybe even less.
This is an almost 10-year old iteration of my 1976, back in its "Bug Killer" days. Note that the clutch cable makes a gentle, swooping, "S" curve. It's still like that today. You can't get an easier cable pull than this. However, the hydro clutch pulls easier.
Furthermore, the clutch operates like a dream hot or cold, stopped, or moving. Goes in and out of neutral effortlessly in all conditions.
I have one minor tweak I want to try, and then I'll be posting a video I'm making of the installation.