For medium shells, I use H3, KP on rice hulls or BP on rice hulls with a small amount of flash 'booster', depending on the strength of break that I desire to achieve.
For my 8-12 inch shells, I use BP on rice hulls or KP on rice hulls, with optional flash 'booster'. In my experience, flash booster is not required for a KP/rice hull burst charge.
Go very easy on the flash booster- only a small amount is needed. You'll be barking mad to use any more than 2 grams of flash powder! Unless you want your stars pulverised to dust, or blown blind.
I gonna be testing one of my 10 inch chrysanthemum shells tonight. I can't wait!

