@liaLast year I had an idea of using a small electric motor with an offset weight like an cell phone vibrator but a little bigger.
I tried this in my board and I can really feel the vibrations on my front footpad. It was wired to a hand held momentary switch just for proof of concept.
I'm not good at electrics to be able to convert the piezo signal to a constant current, so the idea fizzled away.
Maybe I'll resurrect the idea.IMG_7047[1].JPG