I think flipping is your issue as well. I'm going thru the SAME THING. Sometimes I will get better curl and lift at the crown when I flip and sometimes I just don't. I use either deva curl or ouidad products - switch back and forth. Lately when flipping, I have been getting flatter in the back and I have thin hair so it's just ugly. What I haven't tried yet and I'm going to next time is to lay on the bed with my head hanging off the side and trying to diffuse that way. That ought to be a sight! But when I have my hair done at the salon, they have me lean back in the chair while they diffuse and I never get flat so maybe that's the trick??

Natural hair color - dark brunette
Fine, thinish hair/3a, 3b