Toss an ounce of the same hop at 60 and then get a one to three more ounces for dry hopping. Also, I tend to like my IPAs light bodied to let the hops really shine through and since you are using extract it couldn't hurt to toss a bit of sugar in there so it ferments out low. Maybe half pound or a pound of corn sugar. Just an idea, but it depends on how you like your IPAs
I hate Walder Frey...