I tried making something like that work, years ago. The IR solution didn't work for me, probably because of the noise level in the preamp.
Finally, I used a small loudspeaker, directly attached to the torso. That proved much easier to filter/amplify and worked very well. The speaker cone was filled with polystyrene, in order to provide a flat surface.
Not sure this will do in your case, but hey, you never know...