SSP did this in May and I did it about a week ago [look on right of front page]. I did it in 29.5 hours with some navigation errors, could have done on 24 if I had put more effort in. Really nice route.
http://www.forestfreeride.co.uk/I fancy this route:
http://www.scottishmountainbikeguides.com/guided-holidays-scotland/tour-of-the-cairngormsAnd some more inspiration here:
http://sevendeadlyspins.blogspot.com/