I prefer to use Microfibbetts, 2-3 on each side of a small ball of dubbing on my compara-duns. I fish quite a bit on the Delaware and Catskill systems in NY and have learned quite a bit about mayflies which ride flush in the water. I use clumps of elk hair or moose for tails on my parachutes for the extra bouyancy. Another step I take is to take the 2-3 fibers and paste them together with fleximent to create a thicker tail. Truth be told though I don't think it matters too much. I use trailing shucks of antron or z-lon on half my patterns but when using tails, if the Hatch turns into a spinner fall, the comparadun is a fine imatation of both.