Okay, a brief update.
Swapped in an Eclipse trigger off of an AR15 in place of the PDI. Recoil seemed a bit sharper, and the group size opened up. At 25 yards the PDI resulted in 3 rounds touching, which the Eclipse was more like a 1.5"-2.0" group.
Hmmm.
Put the PDI back, and had 3 incidents of the PCC doubling at a couple of matches. Not happy about that, as the last one jammed up the rifle and cost me 17 seconds to clear.
I ran across a Timney AR9 trigger that I had ordered earlier and never got around to trying. Put that in, and took it to the range. Seemed an even better feel than the PDI, and ran smoother. Retained the previous accuracy. No doubling so far. Looks like that's the one that I leave in (well, for now, anyway).
Ah, the saga continues...