The switch to 5" minimum would be to target coho and it would take Chinook that wandered by. Just how good is the black mouth fishing inside Belligham Bay or outer Samish Bay (7C) in August and September?
Without actually seeing the data and the actual days fished it is hard to say if the NI nets take any Stilly Chinook. I suspect that none of the terminal fisheries encounter them except if a fishery is scheduled in 8A before late September. The Fraser sockeye and pink targeted fisheries have more of an opportunity but confining them to 7 and 7A greatly reduces the possibility.
Although I will often rail against the reliance on models without actually looking out the window to see if it is raining, there is no way that any fishery, sport or commercial, could occur in WA without models because of the Sharing and ESA issues. As such, assumptions (that are and have to be data based, supportable, and documented) must be made. As a colleague says "Alls models are wrong but some are useful". A good, logical biologist can poke holes in any model. But the alternatives have just as many holes.
What folks should look at in dealing with the whole PS Chinook (or any ESA species) is how is it doing? Is it recovering? If not, then what you are currently doing is not working and you must get more restrictive over the whole suite of issues, whether harvest or habitat. If improvement is not being made, management is failing.