I am 179-180cm (about 5.9ft) tall. I bought a Thermolite Reactor Compact Plus sleeping bag liner. By specification it is 183cm, (6ft), however I did not count that the "head-end" also wraps one's head. So it feels to me that it is quite short. However, I managed to tighten the strap on the head, so technically I fit into it. Bear in mind that this is the first time I've tried sleeping bag liners, so it might be that I am just not used to it.
Are there any general guidelines for choosing a sleeping bag liner size?