[glend (Glen)]

I have finished off the belt tuning, thinking that it is the best I can do without a new motor pulley. I gave up on the thin aluminium flashing shims, and just went with a piece of 1mm plate under each motor carrier. Can't push it up too far as the belt starts to rub on the motor carrier. I also extended the motor pulley on the shaft as far as I could (this provided about 1mm of extension as well). Photos are attached of DEC and RA. Did a bunch of slewing to check on how the belt was behaving and it looks good, no wobbling and tension is about right. The photos are post the slewing. If yours needs tuning, be aware that the adjustments are very touchy, and you don't want belt tension to get too stiff or loose - the belt is not spring loaded, that's for the worm only.
Of course Celestron should have paid more attention to this aspect of QA, IMHO.