Interesting experience from the dog's point of view. I'm not even sure what the dog sees. Just googled and as I suspected...http://www.vetinfo.com/dogsee.html
"Dogs do not have the ability to focus as well on the shape of objects (their visual acuity is lower). An object a human can see clearly may appear to be blurred to a dog looking at it from the same distance. A rough estimate is that dogs have about 20/75 vision. This means that they can see at 20 feet what a normal human could see clearly at 75 feet
So the dog might not even see the ground below in any discernible way.
The dog holding on might be his need to have his feet on something solid which bothers me a little about the back legs just hanging there.
For the most part my wolfpuppy had to be on solid ground and it took him about 3 years before he'd finally swim in the ocean. I took him as a pup but never forced it. Then one day he just walked in and started swimming. He hated elevators, crouching in them. Same with cars. The only dog I had who hated riding in cars. And he didn't like boating either.
Weird about my last two dogs is that wolfpuppy had no issues at all about walking on docks but hated boats. He liked his feet on something solid that didn't move. While my Weimar loved boats, loved cars. Hopped on or in and wouldn't get out until you took her for a ride. Used to put her paws up on the bow and ride there. But as agile as that dog was in (webbed toes) and on the water, that dog was a complete embarrassment at a slip.
The fucking dog couldn't walk the planked docks, I think, without looking through them. Unsure of her footing, she didn't just crouch, she cowered her way to the boat.
Safety wise, the only thing that bothers me with the kite flying dog is what landings must look like. The web page says they've been at it for 9 years so I guess he's got his routine but I'll bet he's had some close calls, some winds he didn't expect, that put the dog in danger. otherwise, the dog certainly looks comfortable with the experience. Flying dogs. Who knew?