I did a double layer of Warm/Natural in 2 twin quilts. I hand quilted them had zero trouble. I wanted heavy comforter type quilt.
The problem with getting High Loft "Fluffy" batting is that is does NOT last. especially the cotton, it flattens out and thins out after several washings. If you want something to stay warm and last the test of time. i would suggest doing a batting like Warm/natural that is sheet like, and not fiberous and fluffy.
The fluffy high loft Polys or a long stranded poly keep their fluff longer than the cotton, but are not as warm, and too will flatten out over time.
Hope that was helpful