I wouldn't bother with the sub-caliber shot sizes (anything smaller than 000) because of accuracy concerns with handgun length barrels. Triple-ought measures pretty darned close to bore diameter of a .38/.357 so accuracy is surprisingly good.
If you read my other post, you'll notice that when I cut a factory round open there was no wad between shot and powder. The ball fits so close to the inside of the case that powder can't get around it anyway!
Good luck with working up some of these puppies! I bought a five pound bag of Hornady 000Buck balls so I can make more. All of my buddies want some for their bed-gun. Now to figure out a nice low-flash powder to use....