Hmmm, some very good ideas, now you've really got me thinking beyond just the room...
Lavalier mics attached to the shoes with the wire running from the sender unit down the inside of the pants have been the way to go for the past several years.
The cardioid lavaliers are much easier and more effective to use and control than using contact / PZM mics, since mics of any sort placed under the floor have pickup patterns that tend to be too localized so that volume and tone vary widely depending on where you are on the floor as you tap.
Also with under-floor mics having a portable floor is difficult. I often use two 3'x4' "roll-up" tap floors set end to end, with slats 3' floor-wide by 2" per slat, the slats glued to a thick canvas back, so they roll up and roll out quite easily, and with these contact mics are not an option.
I spent over $200 each for the shotgun mics, but for some reason I've been reluctant to spend an equal amount for the lavalier -- which I hadn't really thought about until you said something. I'll have to do some research and see what is commonly used (Savion Glover and Broadway shows use these things all the time), and see what it would cost. Thanks for the nudge...
And yeah, the whole idea of modifying the sound of the taps (after 5 minutes it all sounds the same to an audience) is to use guitar processors, delays, reverbs, synth envelope followers, etc to vary the tap sounds between (and sometimes within) pieces, mostly using midi control through a foot controller. Which I find exciting, especially since I can also process Cajon sounds to set up a live looped drum track, tuba and sax for various lines, etc.
Hmmm... I have an FBQ2496 and also a Behringer Shark, but I've been reluctant to use them in rehearsal since it means I'm hacking out a good portion of my frequency response, thus skewing whatever adjustments I'm testing with the audio processing at that moment. I do expect to use the FBQ2496 for gigs, so I can adjust my sound output to the room, however.
Good questions, good ideas... hmm, any more thoughts and brainstorming would be very welcome.
Okay, nowI have to go on the internet now and do some research about what kind of lavaliers are used by the major tap dancers in shows.