Fuhrmann and Mike: Thank you both!
I hunted with a few drillings for several years 20+ years ago but kept things well under 100 yards, except for a long shot at a cow elk with a double rifle drilling - following what you wrote, Mike, on a 'dead cold' barrel that I had confidence in.
Back at it now, first ever combo gun and I can almost assure you that your advice on using my off hand to rest the barrels in the V has something to do with it. I have not been disciplined on consistency of how I'm lining up for the shot.
Also, I bet you're right on not waiting long enough. Pinky swear, it was at least 15 minutes between shots.
On the claw mounts: since I've had the gun there is the slightest perceptible movement up and down on the front base. It can barely be felt, but it's present. I did remove/replace the scope after the fall and it felt the same and, surprisingly, I took out the last target I had shot at and the post-fall-bullet-placement was within 2" at 200. This further supports your suggestion, Mike, as these shots were a few days apart.

As ever on this forum: thank you for your insights and I'll get back after it and report back. This long weekend may provide some opportunities to head out/back/out/back.

Al