I am walking the Overland Track in late May.
I have a -1C quilt and a +10C quilt and at this stage am carrying both.
According to a formula I found online for calculating the combined temperature rating of two sleeping bags: X - (21-Y)/2
where X is the rating of the thicker bag and Y is the rating of the thinner bag, this gives me a rating for the stacked quilts of -6.5C
Does it sound like a reasonable plan to carry both quilts? I'll be sleeping on a Nemo Tensor pad (uninsulated) and can also pack a silk liner.