Sheila,
My first thought is the old saying, "If it ain't broke, don't fix it!" And
this  mother/baby dyad may very well be breastfeeding fine with good milk
production, wt gain, etc. In that case, I would discontinue the lip
flipping, especially if the baby is not a brand new baby.
That said, in general, I think the  lip should be flanged out.
Mechanically, to make a suction or seal, (for example with a gasket or
suction cup), one needs a smooth, flat, flanged contact.

Laurie Wheeler RN MN IBCLC
GULF COAST, MISSISSIPPI, USA

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