i have an old synthetic moonstone sleeping bag i bought about 10 yrs. ago. i don't remember its temp rating, but i did buy a down liner to extend its range. the liner fits inside the bag on the topside only --- it buttons into loops in the bag --- i haven't seen liners like this in years -- it seems that now the sleeping bag makers think about the sleep systems in terms of stuffing a summer wt. bag into another bag to extend range.
does anyone know how i can find out how many extra degrees of warmth this liner may add to a bag? it's mummy cut, and though i don't use the old moonstone bag anymore, i think the liner would be a great addition to my 32* bag and 0* bag -- all i'd have to do is sew in some loops.