I think about doing the nape of my hair, where it's straight, but it would still be so different from the rest of my hair I'm not sure it would do what I want anyway. I have tight waves/loose curls (and I like them) everywhere else, and have never seen a perm accomplish a big diameter curl like that - plus the texture of the underneath hair is completely different, smooth and limp and much less coarse, so, unless I miss my guess, it would respond more like straight hair to the perm and not hold it well.
Since it's underneath it generally just looks like it's a longer layer.
2c / C / iii (FIA)
Med-Coarse, LowPorosity, NormalElast (LCLF)
Wash: DevaCare Low Poo
Detangle & Rinseout: Walgreens or Sally's Conditioning Balm (always)
Leave-in: DevaCare OneC (budget choice is GFTN)
Style: ReCoil & DevaCare Arc Angel (budget choices are HESMU or Got2BSpikedUp)