I tried to follow your advice in our evening session. I recorded a short piece placing a pair of DPA 4011 cardioid near the right hand side of the piano, kept the mics at the tail, and raised the audience mics up about 9ft in ORTF.
In retrospect, I think this last move might have been a mistake since they sound brighter but less present than when they were wide and low.
Anyway, here is the raw track.
MIX_4