In reply to David Kirsfelds:
I never carry more than a 3/4 mat (if it's out the back of a car, that's another matter....!), so I doubt it's a huge problem. I also tend to sleep on my side slightly curled, so not as long as lying flat on back.
And, as someone mentioned, I tend to put pillow off the top end of mat - fleece, with any spare clothes folded and put inside.
Another option (for warmth, rather than comfort) is to put empty rucksack (or anything similar) under your feet. As long as it's nicely padded between shoulders and hips you should be fine.