The pheasant tail nymph pattern is one of the more classic, “works on any day” flies to have in your box. Pat Dorsey makes a few improvements by adding a mercury bead and a flashback wing case to get some extra attention.
This fly for me took some practice, especially tying it in the smaller sizes. The biggest issues I ran into were that the pheasant tail can be very brittle, and it broke mid-wrap which really screws up the entire fly (since you use the same pheasant tail piece for the tail, body wrap, and legs). The only advice I can give is to go slow and use hackle pliers if you have them.
I ended up tying some really small versions, as I’ve used these as attractor flies in multi-fly nymphing rigs before. Use a size 22 or 24 just above a similarly sized RS2 and you’ll definitely catch those picky trouts!