good luck in trying to find some goat hair long enough! on the rynda, the wing is often up to 7" long! personally i found some a celtic flycraft on 01269 825591
the basic pattern that's used is some brown bucktail about 1/3 the length of the overall dressing (tied on one side of the tube), with a few strands of peacock hearl or crystal flash on top of that and about twice the lenght of the brown bucktail, with the long goat on top of that.
its often fished riffled across the surface, which can be achieved by piercing the tube to one side of the dressing and threading the nylon through that - so use plastic tubes.