Avery New World Porter is one of a few dryhopped porters that comes to mind - should be good, though 1oz/1gal is pretty aggressive.
I was thinking of going with 1/2 an ounce to give it some kick without it being too much.
Kick it in the name of science.
I have not dryhopped with Willamette, but I use a couple ounces real late in my porter.
IMO, I think the "earthy" thing goes well with porter. Let us know how it works out. Science has to be shared.
Oh I shall report back in December with the first taste, err I mean test...