After listening to many such critters on you tube and the Logarhythm I have, I have come to the conclusion that most if not all  have the same problem.  Without added "special effects", they do not sound like basses to me but a foot tapping a hard piece of wood.  So, here's my question for you percussion "Experts".  My idea is to place piezo pickups, likely the jacks that come with 3 disc, on a thinner "soundboard" a certain distance below the thicker top that the food stomps on. Just my theory, but I wonder if I'm on to something and wonder how far below the top it would need to go?  wouldn't really need any bracing but left to vibrate freely like a guitar top.  Would it be based on cubic square inches/feet?  I'm thinking 2" minimum, but then I'm no acoustics expert.  Bottom open? closed? Small sound holes either above or below the soundboard?   I'm thinking 4" total thickness max? 1 1/2" rubber feet on braced corners?