I had really good success with JARS style stonefly nymphs this year. Pretty much like yours, but without the tails and I used a blackish sparkle yarn for the extended body and for the wrapped thorax. I've got to tie some more of them for our winter season which starts Jan 1st.

I also had good success with JARS-style furled extended body nymphs for matching large burrowing mayflies like Isonychia and Brown Drakes.