I'm recently new to the JJ HR 7M, Alto mouthpiece. I've been very happy with the 100th anniversary NY Meyer 6M. I acquired it in #8 also, Using my favorite brand of reed, Fibracell #3.strength. I tried the #8, thinking it would be mostly a case queen for keep sake, because of the much larger tip opening I felt would be of no real benefit to me for routine playing. I was wrong, I did not find the larger tip opening any more difficult to play and it added a noticeable refinement to the quality of my tone that I appreciated and perhaps suggests I may need to move up a little in strength for the #6.
Then comes the JJ HR #7. As described it was immediately even freer blowing than I thought the Meyer was, using the same #3 reed, which I found lined up better and easier on the HR. It is a little brighter also and as described in a JJ demo, I did find the altissimo range easier. It's not an area I've put much effort in yet, but while scaling along in the key of "A", I accidentally found high G#. No doubt there's a difference in the facing curves that accounts for this.
I use a Vandoren optimum ligature which is at the just right fit point and have not bothered to try the ligature that accompanied the mouthpiece. I thought I had found the mouthpiece I'd been looking for in the Meyer NY, but I've taken to the HR pretty strongly, with an occasional trip back to the NY in #8 to finish searching out the enhancement in tone character over the #6. It's not just the sound, there's a noticeable difference in the physiology behind how I play with the #8 in vibrato and embouchure that's working together synergistically.