Before I would drill or enlarge holes in a vintage guitar I would hope for a good sound person and a Sure 57. Piezo sounds no better than an O'plastic. Your guitar of choice is the sound. Undisturbed a saddle/bridge/nut will seat properly in a few decades. Carving the proper footing/fitting of these is a task few folks can achieve. Tuning down when finished playing not only solves the necessity for an eventual neck reset but precludes the need for a "tuner" and self carves over time the top of the saddle/bridge/nut. As for the Radio Shack wireless mike....you can clip the transmitter anywhere on you and clip the mike on your shoulder strap for a combo voice/guitar blend. Next you can use a sound hole cover and hang the mike inside the guitar/mandolin/banjo/etc. I have tried various versions and finally just turned it on and dumped it inside. Some times it rattled so I just shook a few Caribean beats till it settled down. At one point I mounted the mike inside the guitar to the brass bridge plate but the firmness of the mounting muddied the sound. Now I just slip a foam wind screen over the mike to quell the rattle and dump the whole mess inside. The range of this unit out of doors is almost 1/4 mile so I sometimes leave my tape recorder running in my motorhome, plug the receiver in to it and record entire sessions on the QT. With one of those heavy rubber sound hole covers you can walk right up to a very hot voice mike and never get any feedback. I love it! When I remove it I still have the quality vintage acoustic guitar sound I payed dearly for. For under $25 you can afford to experiment with finding the "sweet spot" or in the case of bluegrass the "G" spot sound you prefer.