porco_rosso
Hey ediegus, thank you for your participation! Sorry for not answering yet in the pianoworld thread.
First of all, as I wrote before, I noticed this problem more and more in regular playing and practicing - only after that I tested it systematically with Pianoteq to be certain about the nature of the problem. I am not a trained concert pianist who can play a bombastic ffff on a concert grand, but even me as a late beginner/early intermediate player can reach very high velocities - as it is supposed, thats why they are 128 MIDI velocity steps. Everyone playing classical music will get to literature that demands playing ff+. I really wouldn't say that I push the instruments artificially to its limits.
The settings for the NU1X and Pianoteq: default. Medium touch curve on the NU1X, perfectly straight line as the velocity curve in Pianoteq. But as I wrote before it also happens with the internal voice of the NU1(X).
As vagfilm wrote here and @RIP explained in the pianoworld forum, I do think there is an advantage using a hammer sensor instead/additionally to the key sensor. Kawai wouldn't add the hammer sensor just for fun to increase production costs in their upright silent and hybrid pianos.