This is pretty much exactly what I am trying to do, on the cheap.If you want to subsidise your effort John, then let me know as I am interested too.

The only real experience I had with this type of measurement was at GEC when we were designing the truly horrible IXT telephone, where we had to take "in head" accoustic measurements using a Bruel & Kjaer stereo measurement system, the mike of which was planted inside an accoustically neutral dummy head. We then ran full audio spectrum sweeps (even outside the classic 300 - 3400 Hz telephone audio bandwidth) to asses the audio properties of various bits of the telephone handsets and so forth. The Anechoic chamber became quite popular for private "after hours" testing of headphones and loudspeakers, with one bloke taking his entire stereo in to characterise the system so he could tweak it when he got it home.

I wish I had that dummy head and the measurement set now to do my Mini with. **sigh**. Unlimited tweaking possibilities....