Most of the time when I fish a dropper its an emerger floating in or just under the film. If you're going to fish a nymph, then fish nymphs. Nymphs should be fished along the bottom, that's where fish find them. Once a nymph begins to ascend to the surface it's in a transitional stage and you wouldn't want a bead head on it anyway. If you must fish a tungsten bead head then a yellow or orange stimulator is a good choice as they float well and have the mass to hold the bead head.