Mike - I have an old Freeman loader that uses the V packing. My old neighbor was a machinist and helped me repack the cylinders. We used a length that was longer than the circumference around the rod and cut it to fit. I remember that he cut one end in a swallow tail configuration, and the other end the opposite, so they would fit together. On mine, there was room to stack several pieces of v packing, overlapping the joints so they weren't lined up. It worked good. I used it on a JD with about 1200 PSI hydraulic pressure.
My cylinders did not have a piston in them - only a rod with a large external snap ring to keep the rod in the cylinder.
I would get the packing too large and cut it down. Maybe someone else has a better idea.