I finally got around to doing this and it sure is smooth now! I didn't take the tire off and don't think it would have helped. The problem is that there just isn't much room to work in there under the fender well. Having dual rear remote hydraulics made it a little worse, since the levers got in the way. It took me about 20 minutes to work the cotter pin out. I didn't put it back in, I put a hitch pin clip in place of it in case I have to adjust it again.
The castle nut takes a 7/8" wrench and I had to move the 3pt lever back, put the wrench on the nut, then move the lever forward to loosen the nut. I loosened it 1/3 of a turn.
I attached a picture of it, side view.