I am also quite large-chested (DD/ I don't even know anymore)
one thing that I have noticed is that full length binders work a lot better for me because there's more room to adjust things. I have an underworks full length binder and I have never had any issues with it rolling up (I just tuck it into my jeans and wear a belt)
Of course, I do usually end up double binding ( which is probably really stupid) and even then I don't think I'm completely flat, so I wear at least a button up shirt over it.
I've heard really good things about gc2b as well. Supposedly compared with underworks binders, the arm holes fit a bit better, and there's less "bunching" in the front. I think if I were to get another binder, I'd go with them