"I've never really understood how people use the short mat and find it comfortable, you're legs must drop a couple of inches"
You would think so, but tbh I've never found this a problem at all. There have been occasions I've put clothing and/or a foam mat under my legs, but that was for insulation, not to level the sleeping surface out. I simply don't notice the "drop-off effect" for more than a minute or so after getting into my sleeping bag.