Trutrak - Slo-Syn servo install - how to?

I've got a Trutrack Xcruze AP, and my Slo-syn roll servo has been acting up.

A gentleman here was nice enough to send me a loaner servo to test out.

It's going to be a direct swap, same model, same 9 pin Dsub, same mounting orientation. My question is, how do I clock it? I think the obvious path is to mount it, then power it up before I connect it to the roll column so it finds center?

Once it finds the start position, just hook it up?

You can rotate it by hand to find the center. And you can then check full range stops compared to the actual elevator or aileron stops to be sure the servo is not the limit stop. I do/did the install check with the bolt out to compare and ensure the servo has more travel than the control.

All done by hand.

I can rotate it by hand, but how do I know where center is?