Im a bit of a bodger and I was wondering My local store has a 1 season snugpak synthetic bag rated comfort +11 to +7. Its very light, portable and slinky. It almost has the dimensions of the smaller down bags without the thermal performance. I also noticed that 2 of these were smaller and lighter than a vango 250 rated comfort -4. So much so that I was thinking about getting 2 of them and putting one inside the other to see how far I could push the rating. It isn't exactly rocket science two have got to be much warmer than 1. Has anyone ever tried this?