Ok let see...
normaly i don't get much into that kind of thing, but this too much.
I have been snowboarding for about 20 years, from foot-straps and boards with no edges, or with fin's, to surf board on deep snow ( to have a go), binding with no high backs, just some kind of strap (like on the up foto) sorel boots with duck tape, ski boot's, soft boot's, been snowboarding every where on the planet from Chamonix (my home) to New Zealand, Alaska, Canada, US nort-ouest (big up Mt Baker), Japan, South Am., all Europe...
Been working in the snowboard indus. with Rossignol devl boards, boot's and binding (normal & step-in)
Been snowkiting for 5 year's and kiting for 6, i work with Ozone on snow and water...
Some of my friend's are the best snowkiter's and snowboarder's in the world (GC)...
I have more hrs kiting on any surface than 95% of kiter's out there...
So please trust me, i know what i am speaking about.
DON'T take your high back's off just adjust them with less forward lean and use snowboard boot's for the sake of your feet's and heel's.
Has a ski & snowboard instructor a can tell you (and wee all can) that if at one point you have your legs "straight legs at times to get the thigh muscles stretched out" this is the end you are locking your knees so no more shocks absorbers, and your knee cap's are ready to pop out...
Can't believe that a comp like NSI is going to make such snowkite binding .
This all discussion is going to take all of you guys, more than 20 year in the past, and i think most of your leg's problem's are on too much beer and PC hr's, and not much snow time, i guess.
Any way that is just an advice, if you don't care than "a tomar por culo amigos"
Sorry for my poor english ortho.
Don't tell me to try it please
Francaise "highback" police