After an entire morning of tinkering, I got the knife so it functions properly. Initially, if I tightened the pivot enough to eliminate blade play, there was binding of the blade. If I loosened the pivot enough to eliminate the binding, the pivot was not close to being snug and there was unacceptable horizontal blade play.
I was able to start with the pivot pretty loose and some blade play, then tighten it very slightly. This would cause some mild binding, but it would soon disappear. Then, another tiny fraction of a turn on the pivot screw. Again, some minor binding that would soon go away. Eventually, I got to the point where the blade play was eliminated AND the action was easy enough for the blade to open and close by gravity, like my other AD20.5 knives do. Maybe there was a bit of twist in the aluminum scales?
My only remaining issue is the the pocket clip screws are now too short... they're only catching by a couple of threads. I'm currently searching for some longer ones (as soon as I verify what size the originals are).
I never did get another response from Derrick...