Recently I found a great article in Flyfishing & Tying Journal (Summer 2015) by Boots Allen titled Better Buoyancy for Your Mayfly Emergers. While the article content is outstanding and I'm a believer in the use of foam, the application of Heat Shrink tubing can create a Ever Float Emerger that will out perform any emerger you have ever tied or used.
The materials used are as follows;
Hook - Size 16 Sproat Bend
Thread - 6/0 Olive
Body - Heat Shrink (HS) 1/8 Inch Clear - Colored with Olive Alcohol Ink
Ribbing - Gold Thread
Hackle - Grizzly
Wing - Polypropylene Hair
Tail/Suck - Tail Mono Green or Suck Gray Polypropylene Hair
HS Before Coloring - Hook - HS After Coloring - HS Ready For Hook
The fly above has a tail and no suck. To add a suck replace the 3 green mono with a thin grouping of light gray polypropylene hair. This HS Emerger will float better than one tied using foam because of the air trapped inside and the fact polypropylene is used as the wing. HS can be used to tie any Mayfly - if you want to tie smaller than size 16 you will have to use smaller diameter HS.