The outcome of your trial is really interesting, esp. that you were able to overpower the stiffest tongue on that boot. I don't know your specs, but I am 6'2" and 220 lbs in my boxers, so that boot will likely not cut it for me either. Not sure how that translates to the stiffness of the Krypton Pro with the stiffest tongue and spine widgets in place, but if I find a pair to try, I'll certainly see if they are substantial enough for me.
IIRC, The Krypton can be setup much stiffer than the Flexon/Full Tilt even with the #10 tongue. The secret with the Krypton is the rear spine wedge. The stiffest tongue combined with the rear spine wedge in the stiffest position should be a fairly stiff forward flexing boot (maybe equal to a typical 120-130 flex 2-piece). However, I think there's more to it than just having a stiff forward flex. If there wasn't more to it you wouldn't hear about how there are real skiing differences between similarly stiff flexing boots.
When I said I was able to easily overpower the Flexon with the ZipFit I was specifically referring to how the extra support from the ZipFit (plastic collar and tongue) allowed me to completely collapse the boots' forward flex to the point of my knees practically getting down to my skis. With an Intuition liner you just don't have that much support, so you don't get that much leverage over the front of the boot.