I discovered a new "wrinkle" last week in the whole bag carry question.
Back in the days of lead shot I did all my duck hunting with a 12 SxS muzzleloader, but I wasn't making bags then and I carried everything in my coat pockets. I just re-entered the world of ML duck hunting with ITX shot, but this time with a bag and horn since I make my own now.
In short, what a fiasco! Due to the terrain here we almost never hunt from established blinds, rather we lay flat and cover ourselves, then raise up to shoot while sitting flat on the ground with our legs in front. Trouble is, with the bag at your side and even with the bottom at waist height, the bag varies between in the way and awkward. The horn and shot snake want to roll under you as you lay down and every time you shift, and needs to be even higher when you sit up.
I'm betting from period paintings and hunting methods, folks didn't hunt as we are, so never had to contend with those issues. I'm building a new bag now from which I can detach the strap and tie it between the straps on my waders, along with a loop on the bag through which I can feed the "neck" of the shot snake to keep it in place. I'm also including features for easier management of wads while wearing gloves and for a loose horn to drop into the bag. I can restore the strap for over-the-shoulder carry when I hunt ptarmigan, but I have to do something about laying flat with a bag and horn.
That's my first attempt at a "solution" for the issues, but I'm curious if anyone has seen a bag clearly designed for central carry, rather than over the shoulder. I assume that they had other reasons for carrying one that way, even if they weren't wearing waders!