The tail begins as an I cord with regular increases, using wrap and turns (w/t) to form the curve and show where to sew the back ridge on. I've got a video with a technique to make the horizontal bar caused from a w/t to vanish, another highlighting how to do a rInc, LInc in the same stitch to get your hips started, and then a third detailing out how to do the rapid increases for the hips without stretching your stitching.

This is what you should end up with. (click photos for larger image)

Instructions: