The recipe from Beer Captured by Tess and Mark Szamatulski (they actually own my LHBS in CT) calls for 3 weeks in the secondary. I'll stick with the 3 weeks and see how it works out. It tasted great when I racked over to my secondary last weekend.
I tend to like using Cascade in my American porters, but I'd stay away from Chinook. It's harsh.