Soak it in dawn and cold water until it loosens up then remove all the meat and fat on both sides of the base of the tail, wash again and rinse then tack it down the way you want it to look and add bondo or gorilla glue to the base to keep it from moving around. It might take a week to loosen it up but even if all the feathers fall out they are easy to position the way you want them.

Rich