If this is true the Piezo goes on the bottom?
General mountain dulcimer or music discussions
Nathina, if you play the dulcimer in a traditional style, meaning it sits on your lap, the back cannot vibrate much at all. That is one of the main reasons dulcimers have so much less volume than guitars. The other reason is that the fingerboard traditionally lays right across the top, so the top can't vibrate much at all. One reason some people get dulcimers with a false or galaz bottom is to allow the bottom to vibrate more, getting more volume.
But I don't see this as a choice. Both the top and the bottom vibrate, but both are limited by the structure of the dulcimer. If you want some proof that the top vibrates, check out this video by David Beede demonstrating his decoupled tailpiece . Basically the more restrained the top, the brighter the sound, the less restrained the top, the louder and more mellow is the sound. If you want proof that the bottom vibrates, put it on your lap and strum a chord, then while the chord is sounding, lift the dulcimer up. You will get a burst of volume as the bottom is allowed to vibrate.
I have one dulcimer with a pickup on the bottom and I don't like it very much. To get a decent sound I need to play with an equalizer to get decent separation. The internal pickup I like the best is in my McCafferty dulcimer. It's a K & K Sound twin spot piezo, so there are actually two different spots transmitting sound. Unfortunately, I don't know where those spots are, although I have to correspond with him on something else and I'll try to remember to ask.
If I am not mistaken, you have a pickup that attaches to the outside of the dulcimer. Play around with that, putting it in different places. I think you'll discover a lot about where the most resonant places on your dulcimer are.