Belt slipping off Scout

How do you keep the belt on the Scout from moving it's way up and off the pulley. Is it too loose/tight? Pulley too high/low? Talc or no talc.

I'm using the 300 rpm motor.
Hmm, that's odd. Is there a noticable height difference between the top of the plinth and the top of the motor case? The motor should be no more than about 3mm below the top of the plinth. If the distance is greater, (and the feet are properly installed on the motor case and the cones are square against the plinth), try raising the motor.

The belt is self correcting if placed unevenly around the platter. Even so, when it's completely level it should sit approx 1/3 of the way down. Is this the case?

FWIW-I've never had a problem with my belt.
Sometimes it is, sometimes it's not. The motor is at about the same height as the plinth, however now that I look at I can see that the motor wasn't perfectly level; maybe that was the problem.
I had a similar problem with mine when I first installed it. Make sure there is no twist as you place it around the platter. If you roll it down it may create this problem. Try to stretch it around without contacting the platter. This worked for me.