Mylar Blanket as Underquilt

[ReXwag]

HH has a reflective pad that is wider at the shoulders.

[BigRigRed]

I use reflectics, you can get it as wide and as long as you need it.

[sossukuk]

I had been thinking about using thermowrap. the stuff pot cossies are made from. Its basically bublewrap with outer silver foil on it. that and maybe an old sleeping bag slung underneath.