Thanks Chad. The part I didn't get was not how to do the TX/servo setup or how to adjust the turnbuckle, but what to use as a reference to get it square. Your wall trick got it pretty close, closer than I could get by eye.

It turns out that putting the horn right along the servo is not the right position for this model. I tried that first and everything was off. I went back and looked at the manual. The manual actually shows the servo horn at about 1 O'clock. So I took it out again, went one tooth clockwise and then used subtrim to true up the steering arms. Then I could use the turnbuckles to get the wheels straight. Came out close to the 20mm shown in the manual.

When I ordered parts, I ordered both the arm with inserts and the option part with the built-in 25T spline. I used the option part which seems to work great.

I like having all the good tools and stuff so I will probably end up getting the Hudy Setup System.