Thank you, Craig,
Email to CSLabs is on its way. You can almost predict the answer... They do have a solution for the spindle, the CSMIO-ENC expansion module for threading. It will require, officially, an extra, separate encoder on the spindle axis. But let's see what their answer will be.
In the meantime, my PLC script will have to do. It takes the motor position feedback register, "CSMIO-IP/Feedback Ch[5]" to calculate RPM once per second. It stores the result at mc.mcSpindleSetSensorRPM(). The indication is somewhat unstable, probably caused by timing issues. The script is added here for your entertainment, remember, newbie. I'm certain someone can come up with a better procedure, timing wise.
Mauk