There are several threads here, on raw feeding - one that is currently active you might check out is:
http://www.yorkietalk.com/forums/sho...d.php?t=101885
I don't know about the medallions; but a certain amount of natural fats (that would be in the skin) is essential for balance. In prey-model feeding, folks usually just let the pet's weight determine how much skin is either taken off or left. Pet looking heavy: skin the chicken. Pet needs a few ounces: leave the skin.