Thanks for the links! I had checked out MotoJournalism before, but had not seen The Oasis of My Soul; I'll give it a peruse! In terms of carrying the gear, I definitely won't have it on my back. I've got side bags for most of my equipment, and will probably mount a locking Pelican as a top case for the camera gear. When I want quick access, I'll carry the camera in my tank bag, where there is the least jarring around from the road. I have been reading adventure bike travel ride reports for the last couple years, and have seen many people carry their gear this way with no problems.
In terms of going to a smaller setup, I've certainly thought about it. I think I would really regret not having an SLR with me, as the joy of using it outweighs the weight and size most of the time. Going back to my Europe trip again, I could have carried all my gear in my 40 liter pack, however I brought my 70 so that I could bring the camera and lenses. I'm glad I did.
Thanks again to a fellow rider!
I dont blame you for leaning towards the DSLR instead of the smaller camera. Since you plan to use a pelican case on the top of the rear, thats good. Yes, you're right, many do have a tank bag for convenience. Knowing you will have to make some space compromises and extra expenses (pelican case) to have the camera you want, go for it!