In reply to Tall Clare:
This might be too far to walk, but; take the Lairg Ghru path, cross over the "Cairngorm Club" footbridge and not long after than you come out of the forest and into a bigger open space. I camped near to the river in this area in June; there was another group in the same area but far enough away not to disturb me.
I expected to be midged but wasn't...