Here's some interesting info :
Note that it works by balancing out the bow wave, with an opposite phase wave generated by the bulb. The bulb creates drag in the process, but this is more than compensated for by the reduction in drag along the hull
, resulting from the smoother flow.
Therefore I think they would work best when :
You are generating a large bow wave, so that the bulb can cancel it out.
You have a long hull
, so that the effect of reduced drag along the hull is significant.
Neither of these things is true on a small sailboat.