latest cigar box guitar

Here's a piccy of one of my latest cigarbox guitars. It's tuned to low open E. Neck is mahogany and it has a piezo pup. Bridge and nut are threaded bolts. Strap is hand made from some webbing with strong hessian twine to anchor each end.

I've had a go at a stompbox using a cool looking French butter box. I attached a piezo disk and amped it up but it sounded rubbish. Just a plain tapping sound. I want a deeper thump but as yet don't know how to get it.