From what I understand:
During shiny breeding, 4 IVs will be picked at random (provided there's no braces involved) and of these 4, 2 will be the highest possible while 2 will be averaged.
If that's the case, would that mean that to breed a 5*31 natured shiny comp, I can go with a female 4*31 (without nature) and a 5*31 male with nature, since there are only 2 IVs left that aren't the same/31s? So I could just give the 5*31 natured mon an everstone and get the last needed 31 AND nature.