Just finished an R2R with a group of 35 (28 hikers). Chumley asked on my triplog: With the t-shirts and group of 35, did you have to get a permit? I'm curious about that process since it's a relatively new implementation.

Any hassles from rangers along the way?
I decided to post my response here:
Only 28 hiked (the others were drivers and non-hiking family members/friends). And yes, we got a permit b/c we are generally the rule-following type (though I'm still a little irked about it). Another gal in our group secured the permit, so I'm not certain of how bureaucratic the process was. I'm pretty sure NPS is just happy to issue a permit to (and collect the cash from) anyone who will voluntarily comply, since that's really all they can hope for. I am 100% sure that, absent our t-shirts, there would have been no more basis to stop and question us, as there would have been for anyone else. Even with the shirts, I got zero questions from any rangers, though we passed several. We don't hike en masse--everyone hikes at his/her own pace. At any given time, the biggest "group" hiking together was probably no more than 5. As mentioned in my triplog, the vast majority of my R2R experience was a two-person hike with my 12-year-old daughter. We had folks who finished in under 5.5 hours, and some who finished in 14.5 hours. Some took the side-trip to Ribbon Falls; others didn't. Actually, we got more questions last year, when the permit requirement was first put in place, but didn't even apply to our group.
Honestly, I'm pretty confident that our group of 28 left a lot LESS impact on the canyon than any random selection of 28 other hikers on the trail that day. We caused zero congestion problems, and as far as I can tell, we didn't otherwise "interfere with visitor use" (whatever that means).
I don't like the permit system. I think it only captures inherent "rule followers" like our group (who are generally the same folks that are highly respectful of the canyon to begin with), while the non-rule-following source of most of the problems either: (a) aren't subject to the permit system (i.e., groups of less than 12), or (b) simply ignore the permit system, keep their $175, and continue to trash the canyon.