For a river of that size and flow I would fish my CND Solstice 13'8" 6/7/8 and I'm sure it would be ideal. In fact, there are few rivers where I would opt for something smaller and at that point I'd likely go single-hand Spey casting (see Simon Gawesworth's book / video) with my trusty 9.5 ft 8wt Sage RPL.
I would go bigger though - rivers like the Thompson call for the big guns, 16 ft is barely enough on those real western rivers.
The purpose of Spey casting is to reset the fly at the top of the swing with as little as one motion, sometimes two, while requiring only a small fraction of the backcasting room of overhead casting. Once learned it maximizes the time that the fly is in the water and covers significantly more water than overhead casting. Once mastered it uses very little energy although you may need a hot tub or massage therapy during the learning curve
Good to hear that the Salmon River is becoming swing-friendly... my last visit it was far from it.