Not sure what others' experiences have been, but until lately, I agreed with my buddy, Steve. Tying stone fly patterns seemed to turn out a cool fly, but not much good.
Last Spring, I had a fine, chunky Grayling eat a stone fly pattern.
Last Fall, I hooked (but did not land) the biggest steelhead of my short career on a large stonefly pattern.
Last week, I saw stone fly larvae clinging to a piece of cloth pulled from the Gulkana. The larvae were big, 3/4 inch long and fat, just like the stone fly patterns I was carrying. My daughter tied one on and caught the best Grayling of the trip. They're a large enough morsel to appeal to trout too I bet.
S'pose I'll tie a few more. Some flies I keep for when nothing else is workin. I'll be trying this pattern more often.