I'm having trouble with the battery operated Philips SafeRide LBL: the bracket simply can't keep it level. Even with the knob fully tightened (I used a wrench), the bracket can still be rotated without much effort. I'm using the mandated rubber spacers given the handlebar width (26 mm), and I'd give the 21-25 mm belt a try if only I didn't misplace that.
I suspect the handlebars are part of the problem: even after cleaning with various different products, the powder-coated(?) surface isn't squeaky.
Have you had this problem too, and how did you fix it?