For what it's worth, i just put a cylinder on my 1300 sickle this past weekend.
It worked just fine for several hours until the mount holding the PTO shaft and the drive pulley got bent.
I'm not sure if it was because the spring retainer broke or because the I hit a big hole while maneuvering and working the hydraulics, which caused a sudden "jerk" to my sickle and applied considerable force to the pulley mount.
I heated up the mount with a torch and straightened it up, and I welded a 3/4" plate into the curved section underneath the pulley to strengthen it and keep it from flexing. I also measured the exposed length of the hydraulic shaft with the sickle in the transport position and put a piece of pipe over the hydraulic shaft to keep it from over-retracting. This is just a fail-safe to keep the cylinder itself from bending the mount while raising/storing the sickle.
After my repairs yesterday, I cut several more acres of grass and things work perfectly. I did not use a chain to fix the cam stationery. I did fabricate my own spring retainer and have a fairly high amount of tension on the spring.
I can get pictures, perhaps later today, and post them up.