Hi, there's a post about it on my blog, which I'm not allowed to publicise here.
It's a bit pokey and getting in can be a tyauve if you're a bit on the chubby side, but there is room for two to sleep horizontally and to sit up inside without feeling too cramped. Have stayed there myself and was glad of it, considering the rain outside and my lack of a tent.
Now, keep quiet and don't say a word...
http://cairngormwanderer.wordpress.com/2011/10/08/the-not-so-secret-howff/ There. No-one saw that, did they.