So I am a 3 season camper 95% of the time but occasionally will venture out in the winter for a night if the weather isn't too nasty. I've got a down bag EN rated at 23 degrees and use a silk liner. If I took my 40 degree summer synthetic bad and draped it over the top like a quilt being careful not to compress my down bag would that add much warmth? I also carry a closed cell foam pad to put under my xlite pad. Am I going to freeze to death if it gets down in the teens?