In his(Schollmeyer and Leeson) book he uses 4X tippet for hook sizes above 18 and 5X for 18 and smaller. It says to tie a clinch knot around the middle of a bundle of yarn. There are a few other particulars but that is the meat of it. Fran Betters Piggyback nymph which is similar uses deer hair attached with thread. Tying Emergers has several different variations of these nymphs. It is a great book IMHO.

Buna