We just got back from a ride. It was 1300 km four day camping trip, with approx 500 off road kilometers. From Belgrade to Kopaonik and Pester, than to Bjelasica and off to Montenegro TransEuroTrail. After that, Bosnia and back to Belgrade.
Oleg's bike was set up almost identically, except he was using Giant Loop Siskiyou panniers, his favorite bag. Also, he used generic 10 liters dry bag instead of Fatty tool roll. Using Perun moto 1X90 Lower Side Brackets really helped to position GL panniers perfectly. Also, having 1X90 Side Carriers helped a lot - panniers were resting on the dry bags and were perfectly secure.
This way, we had more than enough room for camping gear, food, water and clothes. And more, all was very accessible and tidy, with plenty of extra room. Bikes performed great, as weight was very centralized. Also, in my case, R80 acted as cushion pillow when I dropped the bike on rocky trails (twice).