I have a 12 degree North River. The factory sez it will run in 4 inches of water - I don't know, and don't plan on finding out. But 8 inches doesn't scare me. On plane the chines are out of the water, so I think I draw about 5 or 6 inches. There is an effect similar to the ground effect in airplanes where in very shallow water of uniform depth, the hull will get more lift than in deeper water. This will let you run over a 4 inch deep bar, but it doesn't help you if you're in 18 inches of water and a rock sticks up to within 4 inches of your hull.

The 12 degree hull gives a reasonable ride in chop, but it's no Grady White. I feel plenty safe in the sound, but on a a rough day its no fun to travel any great distance.

A 14 degree hull will probably be fine in the Cowlitz, Sky or the Skagit as long as the flows are up. It won't be good for the smaller rivers, but it sounds like you might be looking at a larger boat anyway, which would be too much even if you had a flatter hull.