I think the inflatable SUPs and kayaks are as heavy as they are because of the thick layers of vinyl and nylon that prevent punctures and abrasion.
Kitesurfing kites are made of lightweight ripstop polyester, with a super-thin urethane coating, and have an inflated bladder to help hold their shape. That might be more appropriate tech for creating an airplane.
I don't have experience with hard SUPs but have a cheap RetroSpec weekender 10'6" SUP at 17.5lbs - I quickly looked up the weight of similar size composite boards (e.g. Isle 2) and was seeing more like 24lbs. I googled "competition SUP" and found some at 17lbs in the same length as my inflatable, but much narrower and 100lbs lower in max weight capacity than the inflatable SUP of the same weight.
For kayaks, high end drop stitch kayaks are about half the weight of rotomolded plastic ones of the same size, and only slightly heavier than skin on frame kayaks made from exotic materials, which are the lightest kayak technology and slightly lighter overall.
https://repository.tudelft.nl/islandora/object/uuid:306785d0...
https://www.prospective-concepts.ch/html/site_en.htm (click "Projects" > "Air" on the right)
Personally I think this is a technological dead-end, at least for the civil aviation use cases that I understand. The only advantage of an inflatable system is compactness / portability, but since the Inflatoplane, that's been solved in many other ways by rogallo wings, hang glider type wings, paragliders, parachutes, various types of fold-out rigid wings, etc.
And all of the other properties of inflatable wings aren't advantageous other. They're not simpler, lighter, stronger, more durable, or more reliable than the alternative best option, and they don't seem to have a particularly good mix of useful properties to win against the other best alternative for any given use case, even if you assume modern materials and modern techniques.
Discussions are not optimistic, but do invoke some related inflatable craft - https://www.reddit.com/r/WeirdWings/comments/n7a4k1/what_hap...
If I've learned anything from youtube - flying is not an expensive or inaccessible hobby. But safe flying is.
While the pulley system at the root cause of this could be improved, the failure mode of "floppy wing got chopped up by the prop" seems like there could be quite a lot of ways to get there. Dunno what you think we've done in the last 50 years to improve on this situation, but for anything other than an emergency, I wouldn't want to bet my life on a vehicle like this. Also, I'm having trouble picturing an emergency that would be resolved by an inflatable plane.
Nevermind, I've got it. A single container could hold a hundred inflatable airplanes. That'd be a helluva surprise deployment, if you don't value the lives of your pilots.