LOL, most of my kiting skills are for ultra light wind. Many many times I've kited alone because no one else don't want to go because the lack of wind. I've done it for nearly twenty years now and most of it with foil kites, up to 24m. Mostly FS kites, but also many others including several race foil kites from brands like Ozone, PL, Joker, HQ. However I don't do it nearly as much nowadays than I used to do it and I also use mainly LEI kite now - because it is good enough and more reactive to fly.
If you joriws think that Yteri video impresses me that much think again. It is typical mowing the lawn with a big board, nothing really happens. Kites on the beach of course could have been used if they wanted to do so or had skills and preferably big boards like you had. Personally I haven't used doors for years (2012 maybe?) because they are so clumsy but I do have a light wind TT, I guess it is 145x45 size. Using hf of course makes this kind of equipment less important.
If you know how to fly kite and and how to ride a board (keeping it precisely right on the water and riding precisely correct angle to wind) kite significance essentially decreases. I once showed a guy with a 14m LEI (he was lighter weight than me) how to do it when he wasn't able to pull it up (it was a pity because he came to the beach with a bicycle hauling his gear with all difficulties
). Yes it wasn't much of a ride but I did go out and more importantly came back, without walk of shame. It is all about kiting skills. My goal wasn't to embarrass him but to show him it is possible, show how to pull it up with strong long pull and how to use kiteloop start, how to get some speed first, how to not lose ground etc etc..
I also know a local guy who is semi pro, he always uses smaller kites (LEI's) than anyone else and voila - there he goes again. In extreme cases he has been with a 10m kite, others 14m to 17m and couple with 15m Speeds. I think his secret is superb board skills (surfboards and foils), but of course he has excellent hand for kites too.
Unfortunately your weight alone joriws makes real ultra light wind kiting impossible on water. So your doubts for my low wind skills feel a bit funny to me. Do you even know what ultra light wind kiting is? I know what it is but I don't give crazy claims like riding in 4kn or in 6kn. On ice I've done it because then friction is near zero and you don't need power to get going but never on the water, not even with hf because I don't have that good skills with hf nor any desire to go out if wind is that weak.
When people tell their LEI's are falling from the sky and fix is to take a foil kite I shake my head. If you know how to fly a kite keeping it in the air is never an issue with a TT, meaning when using TT is possible in general. For sure if you take a huge foil kite there is an advantage or if you take a big race foil kite there is an advantage, but with a 15m Speed advantage with TT is minimal if it is there at all, compared to good 17m LEI. Board size and rider skill and weight have much more relevance.
On hard surface 15m Speed is more efficient though, then you have time to collect speed with it and push it to higher angles. But does it jump any higher than 17m LEI or even smaller LEI is questionable. No doubt Speed has more hang time, for those lame long jumps. Indeed, what a difference to a 9m LEI which yanks you up and brings you down dynamically, not leaving you hanging there silly. And you have full control and precise feel all the time for what is happening.
Jumping 4-5m is possible when you get some speed, it is more about board and rider than kite thing. With a 17m LEI in 10-12kn I typically get 15-20 ft jumps, if I had better technique perhaps some more could be possible. No big air for sure but if weather is nice - like it often is in low wind days - it is ok. And actually 20ft jumps start to have some feel of flying. For practicing new tricks light wind days are very good because you can push it to the max without much fear from hurting yourself. There is also not much chop when wind is light.