Well, that 3 season Yeti was made for your BB, only weighs 12.5 oz, and will pack down tiny. Just that for your back warmth and a pad or your pack for your leg insulation, and your good to go! And it's has been on sale! $175!
Or heck, the Winter Yeti is only 18 oz and $200 on sale, rated to zero!
For I consider that the sufferings of this present time are not worthy to be compared with the glory that is to be revealed to us....that the creation itself also will be set free from its slavery to corruption into the freedom of the glory of the children of God. For we know that the whole creation groans and suffers the pains of childbirth together until now.