Then, rc, you should be finding a PTC device across the COM (unmarked) and HERM (compressor run). A little bakelite or ceramic looking device. The diagram I found says there is one and there's no note saying it's optional.
Can you check that?
Did you find a wiring diagram and does it show a PTC?
If there is NO PTC, then that one HERM terminal wire should trace to Compressor and all you'd do is add the SPP6e:
With POWER OFF, first short COM and HERM, COM and FAN. Find a secure place for the SPP6e and run its wires toward the Capacitor.
IF THERE ***IS*** a PTC, Then find the leads from the PTC and Wiggle/Pull them off COM and HERM. Replace with the two wires of your SPP6e. Secure the SPP6e in place and you're done. Button'er up and try a test run.
Sounds like the compressor IS PSC as you were told, but that for some reason there's no PTC device as shown in the diagram in that manual I found.