I think the affirmation is there, the Maxi Ball will be fine in the 28 twist, but best twist for that bullet is around 40-48. So don't try to push it too hard.
Simply anecdotal, but the formulas for determining twist are more based on length then weight (although weight is a function of the overall size)
Anyway, you may want to increase the length of the "total spinning body" by using an over powder wad. This may help on sealing as well and you may be able to bump your charge some.
