In the smoothie I bought from Rondo a few years back, I have only shot 1fg and 2fg through it, and have primed with (4fg, 2fg, and even the 1fg)...
I will freely admit that I'm still new to the smoothbore (being a rifleman all my life), and am still looking for a good combination (with and without a patch) - but seems to me .590, .600, and .610 are good starting points with maybe the .610 being best used with the "over powder wad and over naked" ball" wadding, and the .590 and .600 balls being used with a .020 patch (the .590 being the easiest to load with that patch)...
Just my thoughts,,, However,,, there are quite a few here that know a 'lot about loading these "FUN AS ALL GET OUT" smoothbores...