I asked Craig Mathews what his top mayfly adult fly patterns are. He is on a trip right now, but his staff responded:

"I am sure he would say his top 2 patterns are the Sparkle Dun and the Sparkle Spinner".

I wasn't familiar with the Sparkle Spinner. It looks very interesting and is supposed to trap air bubbles?

This photo is from his web site. Think I will have some in my box next trip