I'll bump this thread.
I was surprised at how much crap I could get into my bags. I had shoes/chalkbag, but not rope/rack for this trip, and I could have left a case behind if I wanted, and still had nothing strapped on the outside--but I appreciated being able to easily lock away my riding gear. Carrying rope/rack between two bikes wouldn't be a problem.
Pics parked in the sand at the Tuolumne Meadows campground--note the rock under the stand:
Kinda hard to make out, but see the vertical marks in the tank bag under the word Icon? Bear claw. I got off easy compared to the wagon parked a car over from me...