This info could be useful in other projects, so I put it in its own build page.
Measure the size of the pads to your liking. I used the width of my ruler as a guide and made my pads square. Mark the lines in pencil on the mouse pad.
With the mouse pad on a hard cutting board, use the metal straightedge as a guide and cut the pad with a utility knife. Try to cut through the pad entirely in a single stroke.
We need to set it free from its cold, plastic home. My preferred way to do this is to put it in a vise and squeeze the jaws until the lid pops off:
Be VERY CAREFUL! Wear safety goggles -- the lids sometimes fly across the room. One of these popped straight into my eye; fortunately I *was* wearing safety goggles.
Once you have the case open, gently remove the round piezo element within:
Be careful not to break the wires away from the element.
The smaller footprint of the modified element means less chance of your finger tapping the element directly. They seem to work better if they pick up vibration from a little distance away.
I assume they aren't as "hot" (don't generate as much voltage when tapped), which means less chance of picking up crosstalk from other nearby triggers.
For the piezo element, try to keep it on a corner, away from the middle of the pad:
For the stick-on feet, try to keep them away from the piezo element. This minimizes vibration from other triggers reaching the element.