Taffin is the one the mentions 4227 in his books. 20g is actually a 'standard' load in .45 Colt. Not as much muzzle blast as you might think. I get 1030fps out of my tests. It does leave a few 'granules' hanging around, but I don't mind at all.
Here is an on-line reference. Yes, you can use the H4227 data for IMR 4227. Should use a magnum primer with it for consistency.
A clinger. When guns are outlawed, only outlaws will have guns. Single Action .45 Colt (Sometimes improperly referred to by its alias as the .45 'Long' Colt or .45LC). Don't leave home without it. Ok.... the .44Spec is growing on me ... but the .45 Colt is still king.