Hazmat,
When tying the Stimulator you might want to try with the finished results to look something like this:
http://www.jimsflyco.com/assets/images/stimi1.jpg
http://www.jimsflyco.com/assets/images/stimi2.jpg
It is a little different from the commercialized version popular today. The differences being A dubbed head in front of the thorax hackle, a straight profile, little to no taper on the abdomen and thorax/head and the Wing tied in at the half way point of the hook, do not stack the wing but manually remove any wild hair or close to it. This will give your dressed fly a more realistic silhouette. Remember also that a lot of adult stone flies have a different color abdomen than their thorax/ head undersides. Hope this helps.
Jim