Does that help any? I know it is a bit rough in spots, but you can probably smooth those out while you are cutting it out... I'm not sure how detailed you can get.
Here is a tutorial that I LOVE http://www.melissaclifton.com/tutorial-stencila.html
It shows how to make the stencils with photoshop.
Also, what friggen awesome dogs! I had never heard of the breed before. They are beasts!
By the way, I think you should make the onesies big, like 6-9 months or 12 months. The blank onesies run small, and, to top it off, you get so many 0-3 month onesies at baby showers that they are wearing a new one every day.