To add to what Chuck Brenner said, you need to adjust the linkages so that
the attachment bolts slide out freely  -- and here is the important part --
when the system is pressurized.  I painstakingly adjusted mine, then when I
pressurized the system I discovered that the hydraulic cylinders were just a
hair longer.  (Actually it's the distance between the bolt hole at one end of
the cylinder body and the bolt hole at the rod end which changes.)

Same goes for retraction -- the cylinders will be a different length when
pressurized.

- Rob Wolf