Couple of things for feedback.....used to be a pretty good class V boater...but I got out of the sport b/c I joined the Navy and they are not known for throwing up bases in high gradient, mountain areas and I started to have some back/hip problems (I heard this was the reason Jeff Snyder started striding and, no, I didn't get them running looking glass falls). Well, I just recently got into the SUP thing when I picked up a C4 Vortice. Been on the SUP for about 7 months now....very fun in the flat water.
1) I think you will have a group of us who used to paddle but don't really want to hop on the Hairy stuff any more. I would imagine SUPing down class 2 and 3 would just be pure joy (not that squirting isn't, you can just walk after SUPing). This sport has already done wonders for my back and hip....it really is a great sport for an aging body.....
2) That being said, I truly miss the rivers and the mountains. It would be great to hop on a board and have fun. But I see some problems you might have already worked out..
a) Most of these boards are like fine china compared to a plastic boat...I ABUSED my boats, I've learned the hard way you just can't do that to a board. Infinity shaper Steve Boehme has a carbon fiber version of his nose rider....maybe a carbon fiber version would be a way to go....he used to work with Mike Johnston on sit-on-top surf kayaks (Mike's father, I think, was a legend up on the Kern in the early days).
b) Fins....I was paddling hard on the paddleboard and the board's fin struck a submerged dock post on the Chesapeake....the board stopped and I didn't.......without the fin it is hard to control the board..... I saw Synder striding on the Bottom Moose but I am not sure he could have done it so well with a fin coming out of that inflatable. I don't know if multiple, shorter fins could ease this problem but it is something to address with rocky, shallow rivers.
c) Just like conventional surfers have not embraced the SUP b/c it crowds them out, I can't imagine there will be all peace and brotherhood out on a river like the Ocoee. When I first started paddling it was a very friendly, paternal sport b/c the numbers were growing but hadn't hit the tipping point. When I left, I didn't paddle the Ocoee anymore b/c of a few bad experiences and the Green was getting crowded for a IV/V run. I hope I am wrong about this one.
I'm sure you already know C4 put out an ATB board for whitewater with a little more float and a little more rocker....I have no idea what it is made of and have heard no reviews. I am currently looking into getting Infinity surf to shape a board for me IF I can afford a carbon fiber model and playing around on the rivers.......
All of this being said, I can't imagine anyone is selling a lot with the economy tanking but it is fun to talk about......Good luck, Jimmy Lee