I don't reload but aren't these commonly called duplex loads? A search for that term brings a lot of results.
A duplex load is a mix of powders with different burn rates.
You could always buy another gun to fit your needs. A 28 gauge revolver.
EVERYTHING I read indicated that the patterns were all over the place and nothing consistent enough to think about using on your "fast furries".
If this is something you try by all means please keep the rest of us informed as to how it goes and what loads you are using......(assuming you still have your fingers and eye sight)