As a QX pilot, I'll give you fair warning it's tough going between SEA and PDX...between Horizon commuters, Alaska commuters and then throw in Delta/Skywest/whoever else...it's a crapshoot. Horizon planes have 2 JS's and pilot's can take the aft (FA) JS...but it's tough between the Horizon FA's and then Alaska FA's (which have priority, on our planes...don't get me started on that).
That's been my experience in flying the route...many, many, many times...over the past 8 years.
(The 'Couve is a pretty good area, I lived there when I was based at PDX...I liked it)