I have a WM Megalite (like a wide Summerlite) and it kept me warm into the mid 20s F. even though it's rated to only 30 F. With its continuous baffles I could shake much of the insulation onto the top of the bag for colder weather.

I agree that a wider bag drapes better AND it makes a better quilt when zipped open and used as a quilt. "Quilting" W/ my Megalite is the most comfortable way I've ever slept while backpacking in warm weather. Almost like home when using my old full length Thermarest UL matress.

Eric
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"There are no comfortable backpacks. Some are just less uncomfortable than others."