Get yourself down to a local camera shop (if they have one near you?!) and have a look at a few.....I doubt the shop will mind you trying them on, and you'll get a better idea of what you'll be able to fit in them!![]()
Tamrac expedition series???
I have a bulky Lowepro Mini Trekker AW, its used more as a house to all of my gear when at home - its a bit bulky to take out on shoots. However on big trips its perfect - It fits my body with 70-200 F4 attached with the lens hood left on - just for quick access.
Thats actually quite a small backpack in the grand scheme of things!