It's easy to beagle a mold to get bigger bullets.
The Cast Boolit forum is all over it, but what you're basically doing is putting aluminum tape between the mold halves.
Linky to the .pdf file here.
Sticky at the Cast Boolits forum here.
Once you have your bullets as big as you want them, size them to the size you require. You can either have a stock sizing die opened up, or you can ask Lee to make one whatever size you want. They charge $30.00 for the sizer.
LINKY HERE.