This is the way I do it !

Go to your local auto parts store and get a small container of Body fill and hardener.

Take your fan and skin the tail base out leaving the skin and quills still attached, you have to scrap every quill off, in the middle part there is a large bone that is between the midle quills , take and cut it out, in the end you have a pocket with the quills.
Add Borex to the pocket and then Fan the tail on styrafoam, Mix up a small container of Body fill add the hardener and scoop and place it in the pocket/Base of the tail, make sure you get the body fill on all sides of the tail base.

Once filled , take your hand/fingers and lightly push the fill around and flatten it on the wall side of your tail, so that it sits flush on the wall.

In 10 minutes you are ready to put it on the wall, Make a plaque , the area you are going to screw the tail too needs to be cut out , to allow the body fill to become even with your place. You can take another small peice of material like (Paneling) and glue and screw it over the opening, this gives you a indent area for the base to sit , and screw the tail base to the paneling. You are ready to hang the Tail on your wall ...BT