With moms who are very large I usually suggest wearing sports bras. They
are less restrictive, provide adequate support and are much easier to find
in appropriate sizes. Rather than lifting up the bra to nurse, I suggest
they pull the bra down and use it to help support the larger breast during
feedings. Have had several moms find this a very effective method, but
don't believe I've ever worked with a mom as large as you mention (46HH).