The Chamonix 57s look great. I have the 11x14 and it is sweet. But to significant reduce weight from my present 5x7, I would have to go with the N3...and I am under the redwoods too much to have a horizontal-only 5x7.
I'm 67. My present 5x7 weighs 10 pounds, including the lens (Fuji W 180mm) and darkcloth. I could take a couple pounds off by removing the sliding base of the Eastman View No.2 (a little stability would be lost) and going with a lighter darkcloth. But I'd rather take a couple less pounds of food, skip the tent, whatever. If I reduced the weight of the camera/lens/cloth, I'd probably just use that as an excuse to toss in a couple more film holders. Carbon fiber tripod instead of Al would help. Space in the pack (I don't use the expedition size pack anymore) is more of a premium than weight. The last pack trip was a solo in September. Six pounds of food, 28 pounds of camera gear (nine holders and the tripod was hand-carried). The pack on the hike out weighed more than most folks' going in...so it goes. More leg muscles than brains, I suppose. Now if I only had the lungs/heart of old!
My 4x5 is a Gowland PocketView marketed by Calumet...at 2.5 pounds with the lens it is pretty sweet...if one accepts its limitations then one can hike a little farther.
Some of the older Japanese folding 5x7s might make a good backpacking camera. Perhaps not as versatile as the Chamonix, but having a light-weight camera specifically for backpacking, and also having a more versatile camera for home/car use (Sinar, etc) might be more practical...rather than compromising between both due to weight.
From a previous backpack trip...5x7 platinum print. This was about a 4.5 mile hike in, with the trailhead fairly high up in elevation. I carried the camera on the tripod in my arms...which ended up being no fun, but I had to have room for the two or three pints of beer in the pack. The first few miles were the steepest, of course, and that section also had a lot of down trees across the trail from a fire a couple years earlier. The lake was a welcome sight.