There's basically three adjustments for the belt;
The actual tension, the skew of the rear sprocket in relation to the front and step where the rear sprocket (indeed the whole swing arm and wheel assembly) is offset to the side of the front sprocket.
Skew causes the belt to run off to one side or the other of the rear sprocket when under load. The adjusters should be set so that when the car is on a secure lift with the engine running and in first gear the belt doesn't run hard over to one side or the other. If you've got the two sprockets in line, or at least the planes of the sprockets parallel but he belt is still hard against the side plate of the rear sprocket then you might have to adjust the left-right position of the swingarm using the adjusters on the pivot bearings. Once the skew and step are sorted out then you just need to move the wheel back on the tension adjusters till its tight enough. The Super 3 runs a very high belt tension, and probably the best way to set it is to download the Gates Carbon Drive app and set it to about 75 hertz.
If it still squeals after all that then WD40 on the belt will at least give you peace for a few miles!
