i just completed a top quilt and am going to make two stuff sacs for it. one for long term stowage, and the other really small for backpacking.the quilt will lay flat since the foot box opens up to make the quilt into more of a blanket.so measuring it in the fluffed state is easy. but how do you all figure what the compressed backpack size is? is there a forumla for this? based on the fill number of the down? or the hugely wastefull process of "make it and if it's not small enough, make another, and then another, and then another.." untill you decide that the last is good enought, even if you know in your hart that you could of gotten it smaller still?