Well, with Turbo on my thread I dont even have to answer my own questions! Thanks man! I do think it would be cheaper for someone like buckshot to make a sizing die if you deem it necessary, for me that would be another learning experience in fine machining.
For what it's worth .734 slug will have no issues going through a shotguns massive forcing cone at the end of the chamber, it is no different than sizing boolits for a revolver at .360 and shooting them through a .357 bore.