I have the opposite problem ... my bottom layer is straight and the tops are curly. I just was at a deva salon and they suggested using a hard hold gel, scrunching in with your head flipped over, and then scrunching out the crunch when it's dry. I've tried it a few times at home and it does help. I will say it is still not as curly as the rest but at least I get a little bit of wave to help it blend in. HTH
Hair Type: Combo of 2A, 2B and 2C ... with a weird straight underlayer
Fine, normal porosity, normal elasticity.

Currently using:
Low Poo: Yes To Cucumbers Color Protection Shampoo
Cowash: VO5 Moisture Milks
Styler: KCCC
Gel: Herbal Essences Totally Twisted Gel, Tigi Bed Head Creative Genius gel

Started CG 9/10/13