Was wondering about extending the temperature rating of my speer top blanket to be good to 0 degrees or below i have taken it down to the 20 and 30s with North face midweight base layer, a microfleece or 2, and a light polyester columbia jacket with the lost river 2/3 underquillt. I will probably be spending most of my money on a good full underquilt like winter incubator so trying to use make use with what i have. I also have an old synthetic sleeping bag rated to 40 maybe a little lower (a little heavy though). I heard mention of silk liner, and the sea summit bag liner and weathershields in some other threads. The time i got in to the 20s it was pretty windy and i also had the topquilt inside of sleeping bag and stayed pretty warm. Would some sort of bag liner like the sea to summit and plus my down coat and some more layers be able to get me to 0 or below? Any suggestion? Thanks.