im looking into buying one... ive been looking at Canon Deluxe Photo Backpack 200EG because i like how large it is and how much it can hold...i can bring film and digital and there's enough room for my 70-200mm f/2.8, and it has straps for my tripod. the major drawback to it is that its not weather sealed. the other backpack ive been looking into the the lowepro slingshot but i cant determine the smallest size id have to get in order to fit the 70-200mm (i know the A300 fits it) and they seem very small...but on the other hand, its weather sealed and i like the single strap rather than a normal two strapped backpack. comments? suggestions for a completely different bag? does anyone here have either? love it? hate it?