If you want to quilt further apart, I recommend choosing a different batting. Many Quilters Dream products allow quilting up to 10" apart as does W&N products.
It is the integrity of the entire quilt sandwich that keeps the batting from lumping and shifting and migrating. It needs to actually be stitched to some sort of foundation. So if you are dead set on using 80/20 and not quilting the necessary distance then you can probably stitch the batting to a layer of muslin or inexpensive sheet. But I don't know how nice that would turn out and could be a sandwiching nightmare.
My advice to you is buy a batting that the recommended quilting distance is something you are willing to do or change your quilting plan to match the recommended distance of the batting manufacturer.