My back is a pretzel as well thanks to years of roadracing motorcycles.
IMO, the Hobie Pro Angler is the only way to go. All the real estate you need to move and change positions. I started out in a paddle kayak, and just being committed to the 90* bend at the waist made for some pretty short outings.
Now, 7-8 hour days are the norm. I credit it all to the ability to move around.
Just the ability to get to my knees and arch my back is huge, let alone on the more calm days to really stand up and give the back a good stretching out.
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