I'd like to know how that works. I followed the link and they just look like a power strap to me.
The discussion is referring to the orange shim placed in front of the tongue in the image below.
I can imagine this thing inserted into a soft-flexing boot, with a skier who has lots of dorsiflexion. When the skier loads the front of the cuff while turning (in my imagination), the skier's forward-tilting shin will tilt the tongue forward, and cause the ProFlex to tilt forward along with it. But the shim won't bend. So the entire ProFlex insert as a unit, including its lower part, will tilt forward. That tilt will press the front edge of that lower part downward, grinding down onto the top of the clog, and potentially causing pain on top of the foot.
I'm talking about imagination, not experience. Can anybody here talk about using this shim to stiffen a boot and say whether it caused pressure and/or pain over the instep?
I'm also wondering how effective this insert can be. The forward-flex stiffness of a boot is a function of the spine's ability to flex forward under load, not the tongue's ability to flex forward. The stiffness of the plastic body of the boot surrounding the heel/ankle also plays a role in determining the stiffness of the flex. If that plastic resists deformation, the boot will be very stiff in flex.
I'm a little skeptical of this product since it focuses on the tongue, and I'm hoping someone who has actually used it can post.