Thanks much, LG
Unfortunately, things aren't going well. I'm unwell and wasn't able to participate in the potting-up. My research was ignored and the poor peony was potted up in about 1/2 of the loam from where it was dug, 1/3 of only-partially-decomposed leaf mold, and 1/6 of gravel.
I really can't believe they put the only-partially-decomposed leaf mold in a container. That makes it impossible to maintain good drainage.
So, it's exactly what you DON'T want for potting a Tree Peony.
Needless to say, I'm pretty dismayed.