I'm not sure which bag fits the tiger, but the touratech bag I've got for my F650 has been just great. I've a got a large Mavica, FM2, 50mm, 24 mm, and 300 mm, plus my Psion and some other bits in there, and it's just perfect. I've crashed once with it, and I believe a tank mounted bag is the least vulnerable location on the bike.
As a back pack on it's own merits it's not that great though, and I actually use a seperate backpack for longer walks anyhow.
The map holder on the top of the touratech bag is also extremely useful....
You do have to use the rainguard for dusty conditions though....