Oh the prop adapter doesn't move once installed. I use Loctite on the threads, and then with the set screw besides, it doesn't budge. Often times when I take them off I have to heat them to get them to come loose.

This particular engine was set up to run Gas/Glow, and it doesn't use a Hall sensor. When I use electronic ignition, I make up an adjustable collar that goes around the small diameter of the prop adapter. The magnet goes in the collar, and the timing adjustment is made there. Works fine, and has done so for many years.

AV8TOR