I have a 3/4 length thermarest which cost about forty quid about 20 yrs ago. Although its never been a "problem" as such, I have always regretted not getting the full length one. You have to put up with legs dangling (slightly) over end or build-up alternative height at pillow end. I've always felt it was a false economy whether cost or weight. Self-inflating are generally a good combination of low mass and size for the comfort (better than blow-up reeded which are heavy, or roll-up foam, which are bulky)