in my infinite quilting ignorance, i never thought to ask if 2 layers of batting was ok! i just quilted a throw on my babylock with 2 layers of poly off a bolt that i had on hand. it was beastly to move around, but, never thinking i was breaking any rules, i just made it work.
the throw turned out nice and fluffy--can't wait to get the binding on and get it washed to see how it feels.