Thanks to Craig, I got the HLFB's working on my PMDX-108 Input, Port 2 Pins 6-9. Code like Craig's but adjusted for the Inputs I used, 4 sections of code, one for each axis so I can easily tell which axis errored.
That said, soon as I moved two of the 4 axes I got the error. I hooked the USB cable to the ClearPath's and started their software. I have the ClearPaths set to 6400 counts per rev. which in my system equates to 96000 counts per unit (Inch for me) on X/Y, 153,000 counts per inch on A, and 78222.22222 on Z. The count error was set to 10 in the ClearPath software, a default, I guess. That's ~ .0001" on X/Y/Z, .000065 on A, so I set them to 100 and everything seems OK.
That made me wonder if there's some magic following error percentage one should use, like 1.5%, which is what I have, approximately, arrived at by guess and by gosh? Or something else?
Tom