You really have to know and be realistic about how you sleep. I'm a full-timer side-sleeper, but I have nights where I'm absolutely sure I haven't moved from my mummified position on my back. But crazier things have happened. I've also woken with the soles of my feet together and my knees out to the side (only in a hammock!). Ha ha! This is why I chose a slightly wider and a shorter, but full length (to me) underquilt.

I don't flip around all night, but my various positions in a hammock and the fact that I know having any potential of cold feet in the night will guarantee me a sleepless night made my decision easy.

Hope that helps!

And you can use an UQ a good 50˚ higher than it's rating with a bit of venting.