I tie BWO patterns down to size 24 (26 on a real good day) Smaller than that I don't see well enough to tie, so I buy them.

I used to omit th wings on the 20-24, but I am now convinced that they are a critical strike trigger. I can tie an upright wing made from hackle points in those sizes, but I have trouble finding really good material that small. I sometimes substitite mallard flank.

Recently I have started using synthetic yarn such as Hi-Vis for upright wings. I pick out the yarn fiber until I have an appropriate size bundle, then lash the yarn across the hook in figure 8 wraps, like I was going to tie a spent wing trico. Then I gather the two loose ends and pull up, wrapping the base to form a single upright post. I then put a drop of head cement on the tie in point and let the glue set up a bit. When the glue is fairly tacky I squeeze the base of the post with tweezers and fan the wing into a flat profile. With a few snips I trim the flattened wing into a mayfly upright wing profile. This produces a single upright wing that looks like a mayfly at rest.

For the small flies I have been using UTC 70 denier or Gudebroad 8/0. If I want a very thin profile I use thread alone for the body on anything under size 18. I sometimes add a very small wisp of dubbing for a thorax.