I had what I thought was the same problem with my 0-300D. Thought it was the
seals but now I'm pretty sure its the lower center stud/nut holding the suspect
cylinder to the case. Looks like it leaks through the stud to the outside of
the cylinder o ring then down between the cylinder base and case, right on top
of the pushrod tube seals. I'm thinking that the stud needs to be sealed before
installing the cylinder. Anyone have any thoughts on this or have I just lost
it?

Jim