I have not watched that video, will watch it after work.
First: There is a big difference/variation in "real wind" when measuring ~2.5m above ground (like I do)... It is impossible to compare wind ranges only by a "statement", you need to "see" or better feel the wind to really compare. I meassure at the beach, as far away from trees etc. as possible, holding up for ~30 seconds and give the range I see as a reference. That does not meant that this value is the "REAL WIND" acting on the kite.
I cannot really give the "REAL WIND", sorry.If you are at the coast/sea and meassure 5 knots holding your arm up at the beach you can be quite sure, the wind is stronger than that higher up and further out on the sea!
It's different, to my experience, at lakes and when land kiting. I cannot feel higher winds when the kite is high up. And I sometime even measure higher wind at the beach because of compression effect between trees at some spots.
I use Peak below ~8 knots.
And yes its possible to go lower than soul. 4..5 knots is easy, 3..4 knots is possible. 2..3 knots starts to get really difficult, as it get more and more difficult to keep the kite flying while swimming/climbing on board. Starting from ~5 knots I can kitefoil with normal kitefoil board, only problem is getting the board in correct orientation for start, normal waterstart is difficult, but pushing the board under water and standing up hips deep in water works. But if the wind is really low its mich easier to use Wingfoil board you can stand up on without any wind.
For me there is a big difference between Soul and Peak.
Peak will fly completely stable from 4 knots. Not only parked, but you can move it "freely". You can do dives etc. You can recover after you lost line tension most of the time. But you need shorter backlines than stock do do it.
Soul will fly stable from ~5 knots, BUT in that wind you have to center and control it tightly. It will give trouble when you start to move it. It will fly out of wind window and collapse when line tension is lost, it will roll in tips when flying closed to edge etc. So in that lower range 5..7 knots yes, you can use Soul, but in that range Peak is perfectly easy to ride but Soul is a lot of work. So I prefer Peak. Soul is just very heavy in relation.
Peter
if we add about 3 meters of bridles would be 45m!