Yeah, I've been searching. I had someone's thread printed for a while that used the JL XR's and wanted to PM him. He had an Alpine 7995 and all JL equipment. Mann, it was round filed and now I can't find the thread in a search. Ughh! First one to find something shout. I talked to East Coast Scooby and the depth is within the recommendation as you stated, he recommended trying the provided spacers. Cool guy.
I just got back from listening to the JL's and the MB Quartz PCE316's. Actually pretty similar, the highs are a little more distinct in the MB's I thought. Well time to continue searching. Have a good one!