I could do with getting a new bag, and want one that will cope with all seasons.
I'll be using it on cycle tours and backpacking, so obviously weight and bulk are an issue.
I was looking at a three season bag, a vango, which had it's comfort level at 1 deg and extreme -14 (which I seem to remember reading is the temperature at which you'd die?)

http://www.fieldandtrek.com/vango-ul...075?src=google

The weight and bulk are about right, but what I want to know is how much I can increase its performance by with the addition of a fleece liner (homemade) and wearing clothes.

I understand in extreme conditions you can use a survival bag inside (with no clothes0 as a vapour barrier.

i plan on using a Thermarest mat to insulate against heat loss through the ground, and will carry a full face fleece balaclava for cycling, so can use that to keep heatloss from my head.

I know that having a four season bag is better, maybe an Arctic army bag, but the bulk and weight put me off for situations that I may never encounter, or only encounter once in a while, though I could envisage being out in maybe -3 temps.

Is there the ability to increase the performance of a three season bag as above?