I bet the level would make a big difference as to its difficulty, but the gauge there is hard to go by as there are a bunch of feeder creeks that really add cfs.
IMO, the upper a is MUCH harder than the numbers. The remoteness, continous nature, length, and perhaps most of all, the FRIGID freezing f-ing cold water.
I would try it later in the season, at lower water, and plan it as an overnighter. Going with someone who knows it is not such a bad idea either.
Gorgeous run though, and definitely worth doing. Just be prepared.