Drifter looks. . . well. . . not bad. He walks sound, and moves around the house sound.
I took my mother's low-strength (instead of being instantaneous beeping, you have to hold it on the spot for 3-5 minutes, but it does the job eventually) and today I went through and lasered several spots both underneath the iliopsoas area (belly/groin) and on top of his pelvic region, including his lower back. Then I did a spot on his upper/mid thorasic where he was sore at Northeast Regional, and his left toe/wrist area as well. I also took him for a nice 15-minute leash walk. I don't walk fast enough for him (even though I walk relatively fast) so at my walking speed he walk as well. No sustained trotting. Which, for now, is what I want. When I got back to the driveway I trotted him in a circle both directions. He's still slightly off circling to the right. Really flippin' hard to tell which foot/where but I am still thinking right rear explains the mysteriousness. Circle to the left (this is a maybe 14-foot across circle, radius of my 5-foot leash plus me walking in a little circle in the middle) he appears mostly sound with only a small hitch or two.
So I will keep him on laser and leash walk until seeing the Acciani's on Thursday and get a more solid diagnosis then, but I'm relatively sure it's the iliopsoas. Grr. Hopefully minor like before. Better be.