That's exactly what was hatching, and the trout were definitely feeding on the nymphs. I stood and watched a group of trout actively feeding on the nymphs but totally ignoring the flies on the surface.
That's funny that you recommend an 18 instead of a 12. That was my initial plan, but LRO steered me towards using the larger fly... I'll be up at campsite 30 this weekend, and I'll probably take along some gear and give it another go.
What nymph is used to imitate the blue quills?
I got no style, I'm strictly roots.