I have a rather nice lightweight sleeping mat but it's a rather slippery plastic material, and when camping on a slope tends to slide in my tent. The tent is an old VauDe Hogan, with a synthetic sewn-in groundsheet (the current model is polyester, not sure about mine).
At the weekend I ended up pitched across a slope, and always woke up with the mat trying to slide up against the tent wall. As I was at the beach I had a fairly long proper towel, but that didn't add enough friction when placed underneath - the mat slid on the towel.
So how can I get more friction between the sleeping mat and the groundsheet - without adding lots of weight or bulk, as this is my bike set-up and a foam mat is out of the question.
I've now tagged this ultralight, as space and weight are really tight - that's why I've got such a lightweight mat to start with.