I use Warm and Natural for all my quilts. I have never doubled the batting and others here on this thread have give a number of good reasons to not double it. But my message is that more than one recipient of one of my quilts has commented on how nice and warm it was. I took that as a positive and I don't try to change what is going well. As in all things quilting, the choice is yours and experimenting is how we learn and discover.