Define large...
For no sagging and a bit of puffiness, go with two layers...W&N with wool on top.
My preferences:
For 'special' wall quilts, I use a layer of Warm & Natural (to prevent sagging) topped with a layer of wool (to accent the quilting).
For 'everyday' wall quilts, I just use a single layer of W&N.
For 'small' wall quilts, I mount them on artist's canvas to give them presence.