I was thinking about you and keeping up with the Cajones, as I mentioned I was getting interesting sounds from some of the oak stuff I made. Well I made a small box and engraved a living hinge design most of the way through and then with two 180° bends brought the two ends together. Perhaps it was the tension in the bending or a spring like effect at the bends but the box is incredibly loud and sharp when struck every bit as much as the wooden block from any drum set.
I was thinking on a face that was 19" tall and perhaps 8" between the start of the living hinge bends on either side connecting to the rest of the shape and perhaps something similar in the back.
I think that the oak plywood is the best I know for the sound effect.