Steve:
I owned the Ham IV and I didn't have any mods done. I made sure that when the left paddle was pressed and the rotator was turned all the way CCW or CW, my beam was pointing directly North. I also used to switch my 940 to AM and I'd hear the rotator motor click, when it reached its max rotation on each end. Fun times. LOL but the ez rotator kit for 275 would certainly help.
Mike VO1AX