This is my version of the extended body mayfly dun. I use thin packaging foam, preferably the version with a reinforced plastic on one side (not the stuff I used in this video), it’s more durable and thinner. There are two reasons to tie the extended body around this foam. First, you can use glue without risking to glue the whole thing to the needle (you can very easily pull out the body once it’s done) and secondly, once you pull away the needle it fills the empty space making it durable and at the same time very light and high floating. The power flex super glue stays flexible in contrast to some other superglues. In terms of dubbing for dry flies, I always use CDC, if I can.
This is a general pattern that works down to quite small size, as I have shown in this video. Use more hackle for rapid water and less for slower.