Your hairstyle is adorable! I'm alway trying to get more volume too and it helps when I diffuse upside down. I try to get less frizz though while still adding some height on top. I bought the Curly hair solutions clamps and am still trying to figure out how to use them to get more volume...but so far, I've only managed to get less root curl that way with just a bit more height.
Maybe a thickening product would help?