As a long distance touring cyclist my preference has always been to mount the rear brake towards the front of the bike. I have found this arrangement brings consistant modulation with the front brake. Most importantly the brake is out of the way of my homemade tubular shaped pannier that attaches to the rear seat stays. This pannier is shaped like an upside down "v" and has enough volume to contain my both sleeping bag and tent. BTW no rack is required....
May Your Peals Always Stay in Motion,
Tom Hillman
Fresno CA