Admitted, the project I am currently working on concerns a solid body electric fiddle rather then a guitar, but as I don't seem to be taken too seriously among violin people and the working principles should be the same, I give it a shot here on UG.

The question is; is it true that a piezo pick up should not be mounted on a rigid surface?

Taking a closer look at how PE equiped instruments are designed I see several aternative solutions that all point that way. On my acoustic/electric guitar the PE sits underneath the bridge piece on top of the bridge that readily passes the vibrations through to the sound board. On my current electric fiddle (yes, the infamous $ shaped Stagg and one of the reasons why I am a complete reject in the violin community) the PE cristal is resting in a little plastic trough that separates it from the rigid body. The Line 6 Variax has each of it's six PE's fitted on a tiny airtight chamber (or that's what I'm told. I never took one apart)

When I attempt to reverse engineer all this, I come to think that PE's like the vibrations to pass through, not to stop at the bottom and bounce back to the top, thus causing an unwanted reverb effect. But I really don't know if this assumption holds any truth.

How do you guys fit a PE on a solid body guitar? Or doesn't the problem occur here because the bridge is rigid too? And what if I use a L.R.Baggs style of pick up, where the cristal sits inside the bridge piece instead of lying underneath? Can I mount such a bridge directly on the body?

Any input will be greatly appreciated and the most sensible suggestions will be incorporated in the design.
The problem with mounting a piezo on the surface of a solid body is that the body doesn't vibrate as much as a soundboard does. And the piezo transducer would "surf" these vibrations (meaning, move along with them, instead of getting squashed by them). A piezo emits electricity when it gets banged around, so it has to actually be pinched in between something that vibrates in order to work. Hence why all piezo pickups on solid body guitars sit between the body and bridge, or between the saddle and string. You can mount a transducer pickup on any vibrating surface, though, but it'd be mighty weak on a solid body. Acoustic soundboards are the only proper place to stick one of these.