I love my Surface and I use it in my performance rack.
Since tuning the voice is very important for me, I removed my Freq knob cap.
Have you considered adding a Pitch Lock functionality to Surface? Maybe can be added to the Extras Settings Menu? Seems like the menu is filled already so I would suggest holding Voices button may activate/deactivate this feature.
It would save a lot of sweat in case you accidentally hit the freq knob during the performance.
Thanks in advance,