SH- All the OP rivers have the biggies in them. Some have a higher ratio than others. I would say, if you're looking for a good opportunity for numbers of big fish, the Sol Duc is pretty hard to beat. However, I think there are some neighbor rivers that have less fish but what I believe to be larger strains of steelhead. The Hoh and Bogachiel would be a good example. Also the several rivers just south of there have some true monsters that are nearly unlandable! Native nets have proven that what could be state records are a regular occurance. In one river specifically in that area, I spoke with a tribal woman who is the director of tribal fisheries. She explained that a few weeks prior, a 38 pound steelhead had hit the nets and it wasn't all that uncommon to see fish of this size! Might want to respool and scale up your gear a bit!
Believe it or not, if you work some of the classic big fish water on the Skykomish right before it closes you have a shot at some true giants. About a decade ago, I found one of the most beautiful snow white bellied monsters I've ever laid eyes on. That fish was pushing 30 realistically! ..........and no not Oregon 30.
Robbo- If I had to find a big summer run soon I would think about the Skeena River in the Terrace area. Huge river with fresh Babine, Sustut, Kispiox fish inbound for their tribs. All those fish hug the shoreline and can be caught in the slower water out of the main current. Just bring your A plus game. The largest fish in the world in prime fresh form could be the ultimate challenge. Give Noel Gyger a call and he'll set ya up. His number is 250) 635-2568. Another good choice would be the Dean River if you have the funds. The Thompson river if there is fishable numbers is a good one too for some mammoth size fish!