This is a work in progress...
I have adjusted the tuning a bit. The Bb is now a 4:3 above the F, which makes sense. The B at the end has been updated to an 11:8 over the F, giving the last note a bit more bite. Both changes were only a single step in the 53 TET tuning, but they make a big difference.
Here is a graph of the function table I use to make the finger piano have a more robust sustain. It attenuates the attack, and increases the strength of the later parts of the sound.
More work to do on this.