Naruto - Two Blonds, Two Hokages?!

I will be the first one to confess that I ADORE Naruto time-travel fics, especially the ones where he meets his dad. And of course, they always spar to figure our who's stronger. As a tribute to that genre, here's my vision!

In this, Minato's thinking that he's got the edge with two rasengans, but Naruto's cooking up his most badass improvement on it. Can anyone guess what it is?