I held back from posting my pack and setup because as many of you know, I use a non-photo backpack like Will. My setup is probably not all that relevant for most people. But, since this morphed into how to pack things, here it goes...
First, I think it makes sense to define the standard pack orientation:
Front: The part of the pack you see when you are walking behind someone else looking at their pack.
Back: The part with the suspension that clings to your back.
Top: The part by your head when you are wearing it.
Bottom: The part by your butt.
I use a Mammot Trion Pro 50L. It has a back panel opening like F-Stop and a few other photo backpacks. I really like back panel openings for photography, and would never go back to laying the suspension down in the grass/mud/water/rocks. The pack is designed for ski touring/mountaineering. That's good because it is comfortable, relatively light and designed for lots of movement. That's bad because it means I have to turn it into a photo friendly pack. I've accomplished the photo-specific part with two basic add-ons: The f-stop small-pro ICU, and some goofy little monopod carrying thingy from "Oben". I use it to help hold the tripod in place. Because the pack is designed to carry skis, side straps are plenty beefy to carry a tripod.
Here is the pack with a ruler for reference. About 2 feet tall.
Front:
Back:
This is what it looks like with the back panel open, nothing removed. Micropuff jacket on top, ICU in the middle, filter case in the bottom.
As mentioned above, my lenses are pretty small and light so I don't worry about the orientation. However, I do carry the camera mounted together with the sk60xl. Here, the loupe and 17mm adapter are removed. Note how the camera points up toward the top of the pack to minimize stress from each step.
Here, the camera and sk90mm are removed. Sk35 in the bottom left of the ICU that sits behind the sk90. I use a smorgasbord of dividers from various packs that fit just right to cradle the camera. In fact, I don't I have any f-stop dividers in this ICU; they are a mix of Thinktank and Lowepro, I think.
Tripod attached, and the little Oben tripod pouch.
Here are the weights of everything. Left columns would be the heaviest kit I could take. I would never carry all that stuff. Middle column is more "normal" for me. Maybe the bigger tripod, removing some filters, whatever. My normal carry is right around 20-23 lbs including camera gear, tripod, pack, water and other personal gear. The right columns would be the lightest I would normally do; just under 8 lbs of camera equipment, plus another 10 lbs for tripod, pack and personal stuff. Total just under 19 lbs.
Dave