I for one like the idea of up to 74 inches. I think at that size you might actually see it pop up again, and it shouldnt be rediculously expensive. I havent seen a minimac contest since conception.... heard a lot of talk about it, but never a contest.
As for the practice vs size, IMO it takes a lot less practice with a bigger airplane to make the same score on a manuever. To simply say practice can make you competetive with a .40 sized cap against a 40% Carden is a stretch. Face it, its easier to make a pretty manuever with a bigger airplane. You might be able to take home some hardware in Basic and sometimes in Sportsman, but from there up forget it.