I'm now making armatures available for those who would like to sculpt their dolls in the exact size I have made mine. Watch the video below to see the armature. These are made by hand, so they will ship a day or two after you order.
This armature is for a mermaid that is about the same size as my female fairy. Instructions for sculpting a tail and torso for your mermaid can be found in Tails & Torsos. The arms are left longer than you'll need so you can trim them as desired.
The armature in the video below is for the male, but it gives you an idea of what these are like to handle.