When your drivetrain itself has single-handedly won a regional, you have permission to say you've mastered it.

Nobody has "mastered" any sort of drivetrain. Prime example: Team 254, who has their drivetrain down to a science, and have been iterating new and better versions of it for almost a decade, still has not "mastered" the 6wd. Their's is very good, if not one of the best I've seen, but they are always iterating and improving it year after year.

tl;dr: Build a 4/6/8 wd that outperforms 254, and then you can say you've mastered it and move on.