An easy way to discourage tailgaters, weather you trailering your boat or not, is to gently ease on to the shoulder of the road just enough to let the tires start to throw up some stones, this usually gets peoples attention real quick. I know that you guys with the expensive fiberglass rigs are all about not marring the finish, but with my old aluminum boat that I take into any kind of jungle on the water, I dont to much mind an extra nick or two. What I actually hate worse than tailgaiters is the dad gum idiots that pull right out in front of you when no one else is behind you and then take their sweet time to get up to speed limit or even worse drive below the limit.