As a Life Member of SNM-Sons of Neanderthal Man-I have found the Pletscher racks quite satisfactory on my 3 speeds
. They have a built in reflector/flashing light bracket. They come in two styles,one fastens to the seatpost bolt, the other fastens to the seatstays, a t-brace fastened to the brake bolt and the bolts on the rack will keep it from slipping.