I recently bought a cheap 25F non-mummy bag. I found myself swimming around in it, getting it all tangled up, etc. So, it was back to the mummy bag= 0F + 1 full length thermarest and 1 3/4 length thermarest. Keeps me "cocooned" and less material to push around in the tent on hotter nights. Makes for a comfy night - the bag is cushy, the matts are cushy and I will deal with the extra 2 pounds for the mummy bag and extra mattress. Almost as good as sleeping at home with my wife on our Select-Comfort air bed, of course without any snuggling or a wet 4 year old kicking my kidneys