there is no way i personally believe that is 8 kts. show us some video, of the kite and the wind meter.
one of our beaches here has a huge wind shadow and sitting in the carpark 50m from the water ive often thought its not worth going out. walk 40m to waters edge and it will be 10-13kts, kite out 50m and it will be 25kts.
I am not sure I believe that that pic is actually in 8knts, but anyone saying foils do not have power is wrong. Also different foils can be more or less efficient.
I own a second generation peter lynn Arc 840(11m) and I can fly that kite when others are riding 16m inflatables. I can go just as fast and jump just as high. But the newer arcs have less power per size than inflatables. Same kite from same company but mine gets much better low end.
The Arc is a C shaped kite so with a flatter profile it would be possible to squeeze even more power out of the kite.
The wind range on my kite is 15-30 kph(kilometers per hour) and at 20 kph it has lots of jumping power.
So I could probably do something like that if I had the arc 1400 instead of my little 840.
And I currently also own a RRD type 7 so I fly inflatables and foils.
OK you dont believe the old F-one adds you should, those old kites pulled like a MF! yes they would get you up on a plane in 8kts, straight down wind!
But let me take a crack at the PIX, Its winter/spring in south Africa, cold water in warm air, I personally have been planing jumping in flat water, due to these conditions, this is due to the tempurature inversion at the water surface, may be real light 10m's from the ground but crankin uptop.
I would say at least 15 to 20kts up top.
Chris is a pretty good rider and has always used the Blades (haven't seen him for a while so can't say if he still does) and wake bindings. It's his thing! His style! and he's often very keen to persuade people that that is the best kitesurfing combination there is. Is there some exageration going on with the pic/video? Possibly. There is no doubt that Flexfoils Blade is one of the hiest performance kites out there, but I doubt it's that good.
Sadly, Chris's argument about Blades being the best kites to kitesurf with usually runs into the buffers when, everytime I've seen him out on the water, he's crashed the kite and had to swim in. Same goes for all of the Mini-me Chris's (copy cats) that inhabit the North Kent area.
I'm a kitesurfer not a swimmer, I don't care how efficent the kite is, if it sinks it stinks. End of!