I have the Lowepro Rover AW II, and its waterproof brother, the Dryzone Rover. The lower gear compartment is tall enough to stow either a a 70-200/2.8 or the 100-400L, or both, vertically in the lower gear compartment. Their advantage is that they also have an upper compartment for other items such as large lens hoods, supplies, food/snacks, light jacket, etc. The Rover AW II is also fairly light, at just over three pounds. You can check their dimensions on the Lowepro site, but if I had to guess I'd say that my Rover is about 20 inches tall.
The Tamrac Adventure series also has two compartments, but no real way to stow a tripod except for lashing it underneath the pack (cumbersome and gets in the way). Also, gear compartment opens outward, so if you're not careful things can slide out when open...the Lowepro opens upwards and the only way something can fall out is if you turn the pack upside down while its open. The Tamrac Expedition series are large and fairly heavy...single compartment only, and they'll carry a lot of gear, but that's about it. Picture a padded box with dividers and shoulder straps, and you get an idea of the Expedition. Some people swear by them, but I just don't think that they're that functional (I have an Expedition 7 that I retired after getting the Rovers).