Gary try lowering your air pressure and spraying lighter coats of paint. It may take multiple passes doing it like this, but the lower pressure will help keep the paint from blowing out under the edges of the stencil. Holding your brush back away from the bait will help also.
This is more of a problem with stiff stencils especially on baits with tight contours. The netting we use for scales conforms to the shape of the bait much better than stencils do so it's not as much trouble.
Ben