Piezos with Cajon

Hello, I wonder whether I could get some tips concerning the use of Piezo disks or alike. Earlier I used a microphone to find the ATTACK of each sound I make on the drum, but because of feedback issues, I am now trying to use a piezo to trigger sounds in Supercollider.

I'd like to have the sensor inside the drum which is capable to monitor tinny percussive sounds (fast quiet drumming) and is fast to transmit it to the computer (delay).

I've tried both sides of the piezo taped under the surface, it is not sensitive enough. Shall I go for a smaller mic, or perhaps there is a sensor which could sense the vibration on the wood itself. Any help appreciated.

All the best
Krisztian