Here's an idea for Ya Gunnar :
I will PAY You through pay-pal or other , for your time to do
this experiment for me. Hows $20 an hour sound, with a $100
minimum ?
Take a Flat L shaped aluminum bracket, the with of your foot, that's
the length of your foot on one side , and a bit more length for the shin-bone
side where your calf-mussel is located
THEN
step on it, and take some duck-tape and strap your feet
Solid , so there's NO movement in your ankles.
Now go try to use your Hydrofoil. The only other perimeter that's left,
is the slop in the inter-face between what's left of my real leg and
where the prosthetic contacts it, (it wobbles a bit). Actually, a LOT.
The Only movement that is Absolutely Solid, is where i point my Knee
with my hip, my foot follows with More precision than my real leg had
because of the SS bearings on my steal knee-brace.
I recommend that Ya try your Strapped surfboard First ...
Bille