Expand the cylinder so the shaft is fully extended, using a hydraulic pump.
Weld a 3.5" piece of 1.5" DOM roundstock inside of the tubing at the end of the shaft
Take care that the top of the shaft doesn't get hot; there is a rubber seal between that and the cylinder that will melt and cause leaking if you're not careful. If it starts getting warm, dunk the shaft in water to cool it down.
Step #4: Tack the Lower Press Foot to the Cylinder
Weld the nut in the corner of the lower press plate, as shown. This should be on the opposite side of the ports of the cylinder, flush with the press foot, and as near to the corner as you can get it. It can even hang off a bit.