I did that once about 20 yrs ago for my mother. I made a quilt out of polyester squares, used 2 ploy batts, cut off the extra and realized that the two pieces were big enough to make another layer. So i basted them together and added them as a third layer. (Her house was old, no insulation and drafty, she used to complain about being cold at night).
When I asked her how it was working out, she said it was too hot to use. So, I have never done that again. I hand tied it, so I don't know how a machine will handle it. Although, I did sew the binding on by hand, and had no problem with that.