I’d advise you to test your theory of the sponsons being “suffcient in case of a capsize.” While they may offer enough buoyancy to keep the kayak floating with you out of it, the boat will fill with many gallons of water in the absence of flotation bags. It’s kind of a misnomer to call them “flotation bags” because their main benefit is displacing water volume so that the boat doesn’t swamp. It is very difficult, in many cases impossible, to re-enter even a half flooded kayak with no bulkheads and it takes enormous effort and time to hand pump that much water out. If you are with other paddlers who have practiced assisted rescue, you could get them to help you lift and drain it. But that is still an effort that can be mitigated just by having the float bags filling the bow and stern
I recently practiced self and assisted rescues with skin on frame kayaks at the Michigan Qajaq Training camp last August and again in October at the Delmarva Greenland skills camp. Even though we were using skin on frames with flotation bags filling in most of the bow and stern, it still takes effort even in shallow flat conditions to get one drained so you can re-enter after a capsize.
And I can attest to the difficulty I have described from an outing a few years ago when I was in a rush to get out on the water after spending time setting up one of my folders and outfitting it and one of my hardshells to get my cousins launched along a harbor of Lake Erie. Since we were only going to be near shore, conditions were calm and we planned to be out for a short time I decided not to bother with the float bags or my spray skirt in my 18’ skin on frame kayak. We’d only been paddling about 15 minutes when the wind picked up and it got very choppy. I had made the mistake of putting a thin foam pad under my butt on top of the usual 1/2" Ensolite pad and just that little elevation in my center of gravity had changed my balance relationship with that narrow boat (which I had been paddling for 10 years and was otherwise very steady in). One of the cousins shouted something behind me and, fearing they were in trouble, I abruptly twisted around to see them and suddenly found myself upside down. Without the skirt I had to wet exit, and without the float bags, the boat rapidly swamped. I was unable to right it myself because of the weight of the water in it and being in deep water so I had no leverage – neither fellow paddler had any experience with assisting so the best option for me was to just swim the upside down boat to shore, which fortunately was only about 100 yards. Felt very dumb about the blunder and have not launched without spray skirt and float bags since.