if u watch d video minato said it would be un wise to seal something with this much chakra into a baby.so he had to remove some so that he can seal it in naruto.naruto still a baby wouldnt enough chakra to keep something dat large so removing de chakra was basically to weaking kurama for dat period of time so dat before kurama can decide to fight it back the seal would have been solid to curtail the tailed beast.