If you're gonna go the whole lightweight bike approach - surely soft panniers are far more sensible? Apart from the extra weight they are far less crash worthy in proper offs and also get in the way when off-roading. Take a look at the ortlieb panniers or get yourself a set of kriegas and a roll bag.
I didn't try them, they had too much play in the brackets and since I'm away with another three bikers from tomorrow I didn't want to be the one that breaks down - especially since the others are 1200's.