BTW, my hydro port fill plug is hand tight, so I just disconnect the hose and unscrew the fitting and add fluid at will.
Now that you mention it, that is the way it should be. Since it is only a return line, through what used to be a breather, it should not need to be that tight.
I had my kit waiting on me when I got home this weekend. I think it may have been for a different model, though. When I installed it, I had to trim the new breather since it would contact the housing behind it when I screwed it on. Also, the plug to replace the old breather did not bottom on the o-ring. The threads in the full tube did not go deep enough. I tightened it enough to avoid leaks but, now that I consider your post, I guess I did not need to tighten it that tight. I'll either get the dealer to send me the correct one, or chuck the one I have in my lathe and shorten it so that the o-ring will seat and I can leave it installed loosely. There was a little powder coat blow over in the top of the threads, by the way.
After installing the kit, I did notice an improvement. I won't claim that it was any stronger, since that could be placebo-effect, but it did feel that way. I finished up a stump job I had left done and was struggling some with, an took care of it in just a few bites, without so much as a grunt on the part of the backhoe. The cooler temperature of the lines was unquestionable, though, and I noticed that the operation was smoother - less jerky on small movements.
I think I am going to reconfigure the return fitting into a T, though. Now that the return line is not plugged into the detented remote, throwing the remote lever the wrong way will dead-head it the same way as having nothing plugged into that remote at all. So, I will want to put a second QD there so I can run the short loop line to it so the fluid has somewhere to go if I accidentally bump the lever.
As far as filling the hydro reservoir- has anyone considered running it in through a line with a male QD end on it? It may take a while to run 11 gallons through that small orifice, but you wouldn't have to disconnect anything.