I think I would describe the SOTAR design as a 'two chamber annular construction'...
FWIW...I run a single chamber 12' x 22". To me the decision comes down to simple stats. The thing you are trying to protect against with a dual chamber design is a rapid deflation event. A puncture in the neighborhood of 12" or longer. Anything less than that will deflate slow enough to get off the river.
I have run ~20,000 river miles and had 2 rapid deflation events. This works out nicely to a 1% chance of occurrence on a 100 mile river trip (actually seems a bit high, chances probably do go up for heavy loads, Saturn rafts, more Class IV, more technical runs, etc...). Anyway, most boaters probably will experience one to a few of these over a lifetime of avid boating...
After this it becomes a personal risk/reward calculation. Has anyone experienced this type of event on a single chamber cat or know of anyone? How did it end up? I always figure I have better than 50/50 odds of making it to shore by the time the deflated tube sinks. Staying with the one tube until safety boat can go downstream with you and pull you into eddy or shore picks up the rest. Seems like there is another <1% chance that you will have to abandon ship, swim, and the boat will flush with all your gear necessitating a hike out. Still not that bad of a worst case...
Has anyone thought about what they would do when the oar on the sunken side is useless?
- Grab the flipline from the deflated tube and try to counter balance off the good one similar to a mid-current reflip?
- Grab the oar off the deflated tube and put across the front of two tubes on buddy's boat (T-rescue style), thus suspending the sunken tube by the oar tether?
Total thread hijack at this point....at least nobody is rationalizing why they love to bring the kitchen sink.