masking teardrops on Harley tanks

[TWISTED]

I was working on a paint job today and was thinking there has to be a better way to mask off teardrops (sides of tanks usually how Harley does thier factory paint schemes).
I have always eyeballed it. Takes a lot of practice. I drag my pinky around the outside of the tank and lightly mark with chalk where to tape it off.
Any one have other methods?

 

[DDG]

What I did on one set I did like that was to lay
out one side make a rubbing and the pounce it.
Place it on other side then rub with chalk
bag and used the chalk pattern as a guide.
Came out great. It's exactly like laying out flames using this technique, I'm sure you've seen it before.
Dirt