[sawdustdad]

I think it's important for the trunnion "square" hole to be the proper dimensions so the springs apply the correct force. Welding just the corners might not bring the other dimensions into spec. I have repaired several, used keystock for two, but have cut off the old "square" and welded on a replacement for the three most recent repairs. I removed the shaft from the hydro to weld the new square on, but even that weld could be done with wet rags on the arm with the hydro assembled. Just make sure your ground clamp is on the arm, not somewhere else on the hydro.