Cutting the ignition circuits separately, with a bit of time in between, was indeed already suggested in #52. I didn't think to mention reducing to idle, thinking that self-evident, but I now realise it isn't: from the few times I was a passenger behind a Lyco/Conti, I remember they are stopped by cutting the mixture, at fairly high rev (1200 rpm comes to mind?)
But yes, surely, slow the Rotax to idle before stopping it, that will bring less stress on the gearbox - even with a slipper clutch installed, as it should be.
Edit: idle on my 912UL is much lower than 2000, perhaps 1300 or 1400 rpm depending on temperature. The one thing I do take care about is to run it fast enough when very cold i.e. after the first start of the day. Sometimes as high as 3000 rpm, for the first few seconds, then gradually reducing.