doc holiday13
WKR
yes I do understand a mummy is more heat efficient, but the extra "space" you refer to is hardly quantifiable in terms of packed up volum. I haven't seen one these quilts in person but I imagine they're just as bulky and have even more heat voids than a rectangular.A mummy shape is more heat efficient. As a result of the extra space in a rectangular bag, you generally will want to have a warmer bag than you need and end up with a whole lot of sleeping bag to haul around.
My down rectangle is super light and packs just as small as my wifes mummy bag.. the benefit of a rectangle over a quilt would be the lower chance of drafting