Hooboy, that's some load. I guess step 1 is decding how you prefer to carry it--across the shoulder, clipped to the hip belt, strapped in front of the chest. Load control-wise, only the last makes much sense to me for several pounds of camera+lens kept at the ready. A chest pack should include a raincover that can be deployed for conditions or dripping sweat. But it will be really bulky for a FF DSLR. A simple chest harness would avoid the bulk, but would leave it open to the elements.

I don't know that backpack but if the hip belt is quite stout, you might be able to use something like a Keyhole system.

Keyhole

When I was young and had much more energy I once carried a Hasselblad kit backpacking. It was necessarily stowed in the pack on the trail, and I only used it in camp and while day-tripping. The shots were nice but never again.

If I were a truly gung ho landscapist, I'd get a seco... no, third mortgage and an M9, or go mid-format. A simple belt pouch and Bob's your uncle. The NEX7 seems to be a reasonable M9 substitute at a fraction of the price, and is even smaller. The running review at Luminous Landscape has been a real eye-opener. I'm of the view that the digital market has matured to the point big dslrs only make sense for sports and wildlife. Everything else can be done as well or better with gear much smaller and lighter. (But that's a different conversation.)

Cheers,