Casted on YouTube.

I actually did do a 3 Rapier start about a week ago, but it was against Shields on a tiny map so it wasn't hard to shut down. I was also too timid with it, because it apparently had potential according to the chat, but it needs the right placement of Lotuses to defend while the Rapiers are harassing.

I'd have to do some math, but 2 Rapiers might be a better option.

Of course, there's also Comnapping or Gnat prison, but those are really annoying, and the latter can fail pretty hard if the Gnats are unlucky with shot deviation.

I believe Gunship starts are more about slowing down enemy expansion, rapidly expanding, then transitioning quickly.

Gunships, especially Rapiers, are cheap and effective defensive forces.

Building one before expanding, using it as mobile defense, seems like a pretty effective tactic. Its a bit more difficult against ducks because they are particularly good against gunships, but I believe they outrange them sufficiently that it is pretty workable.

http://zero-k.info/Battles/Detail/286314

That is my best game as a Gunship start, it might be a reasonable example.