It's been a couple of weeks, did you start already?
I'm also in Oregon, and the same boat. Last year I grew some photos and some autos, this year I'm going all autos. The biggest lesson I learned last year is that light matters... ya, sounds pretty obvious, but the autos I grew were more sensitive/reactive to the amount of direct sunlight they got than photos were. So if you are looking for big plants, hopefully your grow spot will net them at least 8 hours of direct sunlight a day.
There are other things I learned, like cool weather (like this week!) can slow them down and make them smaller overall, so if you have a greenhouse or cold frame, that would be a good way to get them started -- or just wait another week or two. That said, our cool Oregon nights might slow them down too, making our ultimate potential less than someone from say SoCal.
Are you planning on growing in pots or in the ground? I did both last summer, but one plant (Berry Ryder) was twice as big as the others and it was in the ground -- it also took 14 weeks to finish! I'm sure the size (finished at about 4' tall) had mostly to do with genetics, but I also suspect that it would not have reached it's full potential if it weren't in the ground, so this year most of mine are in the ground. It also makes watering much easier.
I did start them indoors, and learned some tricks after the fact for what I should have done in terms of starting them indoors and then putting them outside in the ground (or bigger pots) with the least shock. I won't make this post any longer... but let me know if you want to know about them.