Del Potro to beat Federer from 1-0 down

As I write, Del Potro has just broken Federer to come back to 5-5 in the second set of his US Open Final. He's a set down after losing the first 6-3, but is now giving as good as he gets, and 8.0 is miles too big for him to beat the mighty Fed Express. He's a hard hitting machine with a huge forehand, and I think the 20 year old Argentine has come of age. I want £20 Del Potro at 8.0.