Thanks for confirming that. I browsed products and illustrations by Renishaw, Avago, and AMS and came to the same conclusion. It seems adjustable magnet distance is not provided as a routine feature. Getting that distance set accurately will be fairly easy in my design, so all I will need to know is what distance to shoot for. I have a test fixture I can use to determine that. One big variable will be the PCB thickness. Ideally, I would have gotten a single-sided board with solder mask only on the top side. I know how to get that done at OshPark, but it can raise questions. So, for the batch I just ordered, I got double-sided boards with solder mask on both sides. For $9 for 3 boards, it will not be a big loss. Besides, I think I will be changing the lead-out design anyway.
The entire unit is made of 6061 aluminum. The magnet will be in a recess and retained with a low-temp cyanoacrylic adhesive.
John