I've adjusted the best I can for now (both the 3 screws and end-play).
I attempted to set backlash during daytime at 8x speed. Counted seconds until I detected movement. Figured each second at 8x is 120 arc-seconds.
Right now I've got the DEC set for 1200 and RA set for 400. I fine-tuned such that tapping didn't move.
Now I did this at 8x rather than Howard's recommended 0.5x !!
I'll see how GoTo accuracy is...