I have commandeered the wiring that would normally go to the old Benmar controller in the cockpit to carry the power to the ST5000, and to carry clutch actuation and drive signals from the ST5000 back to the drive, using the same wires that carried those functions with the Benmar controller. It's that fat grey wire going to the ST5000. By doing so, I eliminate the need to run a new wire.
I have to have the compass hooked up in order to get the ST5000 to run; that's it on the step above the ST5000. But I do not have the rudder sensor hooked up, so the autopilot will eventually alarm that it cannot see rudder movement, and fall back to standby mode.
Nevertheless, when I turn the compass, the ST5000 will drive the motor back and forth, appropriately, pulse-width modulated, and the limit switches in the drive stop movement when they should. It's all good.
This completes what I originally called Trial install #1.
I will write up the wiring changes required inside the drive (very few, other than the required removal of the original mechanical relays), and provide a detailed schematic. Both are partially complete right now.