Looking at an old edition of the Orvis Pattern Index, it looks like a lot of their flies #20 and smaller don't have upright wings.

At what point do you stop tying in the upright wings on dry flies?

For that matter, what is the smallest that you tie dries to vs. buying them?

Also, when do you start using thread to make the body of a dry vs. a dubbed body? What size thread do you use?