I haven't noticed any noise that I could attribute to the belt slipping, even though I do run the belt fairly loose as recommended by SuperMax. I do get some knocking sounds while tootling around at low speed - these I've attributed to the NVH bracket bouncing up and down and coming into contact with the chassis (or some other immovable object). I have no evidence for this - just a feeling.
Early 2012 model with Centa, SuperMax pulley & NVH kit.
