I’ve never recorded an orchestra, but I’ve heard good things about using a dummy head. I once read this rant by an old English guy who swore by it (can’t remember his name). He was a serious professional with many years blah blah blah.
Anyway, he basically took a flat piece of wood – more or less following the outline of a head as seen from above – then he added 2 short vertical walls to the top. One wall ran down the center, separating left from right. The other ran from “ear” to “ear”, separating front from back. Therefore he had 4 sectors, each in the acoustic shadow of its neighbors, thanks to the walls. He placed a mic in each quadrant, pointing away from the center. I think he used omnis? Anyway, he mounted this assemblage on a mic stand and placed it at a prime seat location, about head height, maybe a bit higher. So it was cheap and easy to do. He said it captured the hall ambience wonderfully, and since the orchestra itself had learned to play to that hall, why not try to capture that? He was a big fan of natural sound.
If I were in your shoes, I’d give his method a try. (Perhaps because I’ve worked many video gigs with 2 camera, and thus 4 mic inputs, we never had too much time for setup, and we needed to keep it cheap.) Just a thought.