If you want big flavor/aroma, shoot for 10 minutes or less on the boil. If you're a hophead, you can't really go too big here, in my opinion. You aren't getting much bittering, and any flavor or aroma volatiles will fade, so even if they're strong to begin with, they won't be, given enough time.
For dry hops on my hoppier beers, I tend to go around .5 oz/gallon of pellet hops.
You also might consider a hop stand, where you put hops in during the early part of the chilling/whirlpooling process. Purportedly, this lends a nice flavor and aroma component because the wort isn't boiling and driving of the volatile oils as aggressively. I haven't yet tried this method, but the theory makes sense in my head.
