2stubborn2quit said..
Noooooo.
Two tethers is just plain stupid.
Practise with a kite that is well within its wind range. It is so easy.
If you kite is over powered, don't blame the launch method, try looking around at the other guys of similar weight and put up that kite or one size smaller.
If you are a newbie don't just stick up your kite that is bigger than everyone else's because that's all you have.
Lastly if in doubt ask a bloke who is wearing a bucket hat and looks like they know what they are doing.
Don't ask:
People with crash helmets
Kiters with boardies over their wetties
Kiters with really bright coloured boots
Euros
Middle aged men with old crappy gear.
It was a hypothetical, as I am curious as to what it would do, although not enough to actually try it.
I am guessing that if the kite did loft you that a fixed tether would instantly flag out the kite even as you started to get pulled by it, which would avoid you getting lofted. I think that is how the mechanics would work.
I think I
am the guy wearing the bucket hat, and if it wasn't for the way I can't put my board on my feet, or carry someone else's board while kiting, you would probably assume on sight that I know what I am doing

Obviously not all the time.
The example I used was a bit of a weird one. The kite I had this happen to was meant to use a bar that had line lengths that were not equal on the front lines and the steering lines. When we launched it with a bar that has equal length lines it was like it was set to more than maximum power, because the front lines were 6 inches longer than the rear ones. Hence the excess power.
I am around 100kgs, so finding similar weight people at the beach can sometimes be a challenge. I tend to figure out what the lighter people are kiting with and base my estimate on that. So far, so good, other than the dodgy kite example.