The best way to keep your boat safe is on a trailer with a rubber tire or two under the tongue. If your boat isn't grounded, it will be less likely to be struck. If that isn't possible, then maybe a lightning rod on top would work. It would have to be very pointed and have a substantially strong conduit running to the ground. Insulated copper is good and readily available. Just remember, lightning is an imbalance in charge in the atmosphere. So it's looking to get to the ground where it can be disappated radially. Round insulators are unlikely to get struck. If you actually look at accident reports involving lightning, you'll notice that the strike wasn't at the highest object. Most sailboats are struck at rigging points where there are pointed objects. Not usually the very top of the mast. Its funny a condom was brought up because that is the exact shape that you would need to be completely safe...no pun intended. Even setting your boat on tires would help some. Hope this helps!

Reid