1. My buddies who wear heavy reservoir/cargo systems often have a blinky light fastened to their backpacks. It's way up at the top and when they ride it mostly shines up into the air.
2. These things can get so bulky that they are aerodynamic bricks. Buddy of mine likes to get aero on long downhills but I finally had to show him a picture of his silly reality. When down in the drops, his backpack actually extended higher then his helmet does when riding in the drops but not crouched.
3. I still dont get the point of going weight weenie, reducing one's steed by a few pounds, if you're going to carry a hydration and cargo backpack.
My recumbent has all the carrying capacity I need. Nice backrest has lots of room.
david boise ID