Thank you all for your thoughts. Ok, so maybe I'm nuts but I have the mini-trekkar and the equipment I really always carry is: 40D, 70-200 f/4L, 24-105 f/4L, 17-40
f/4L, 100m f/2.8 macro, 100-400, 1.4 ext., Kenko Extension Tubes,
430ex, fliters and accessories. The 100-400 goes on an outside pouch and the flash goes in the outside pocket, everything else fits. I haven't put it on a scale, but I doubt it's 40lbs. And if it is, I'm in better shape than I give myself credit. I put a bottle of water in the big pouch with the McClamp and strap my coat or extra layers to the outside. I want a more efficient set up so I can get rid of the outside stuff and maybe add 1 lens or body. I really, truly don't have plans to do Yellowstone with this set up but on any given daytrip end up using just about everything in the bag at least once. The Nature Trekkar seems like it gets me close except for the waist belt that can't be hidden for flights. Anything bigger than the Nature Trekkar in the LowePro line seems like it puts me at risk of not getting on the airplane at all. []. I guess now that I think about it I always still have the mini-trekkar as a fallback plan in that regard.