I have been researching adding power steering to my Kubota B8200 and came across your prior posts, fatjay. I have purchased the same steering column and also got the original cylinder with it. Did you loop the aux output back to the return line? Thanks for any extra advice you may be able to provide with the fabrication process that you have changed after the completion of your upgrade.
On page 2 there's the pictures of the aux output being looped back in. It's been a few years and I can't remember the exact details, but basically if you go to full lock, you'll dead head the pump and blow something, so don't do that. The cylinder that I bought seems to be perfect, same with mounting holes. Still running it regularly without issue so I can't complain. No leaks effortless steering. I did have to shorten the whole shaft by about 2". I used a pair of pipe cutters to cut 2" out of the outer shaft and welded it back together. Could have duct taped it honestly. Then I cut the inner shaft that turns to length, cut the old splined shaft off the old steering column off and welded that on so I'd have the splines and could weld the origional wheel back on. Looks and feels like OEM.