Plus, hides shrink when they're tanned, so, since the manikin is made to represent the carcass, if you take the measurements over the fur, you've ADDED girth, length, whatever because of the skin and fur, and then your cape / hide shrinks making it smaller (thus SUBTRACTING girth, length, whatever, from the hide). So, theoretically, you have a hide that wouldn't fit over the original, actual carcass let alone a manikin that is actually bigger than the original carcass because you took the measurements over the fur.
So, the taxidermist actually has to stretch the tanned hide BEYOND what it was when the animal was alive.
"Knowing when to shoot and when to wait is one sign of maturity in a bowhunter. Be patient and pick your aim point carefully." ~ Randy Ulmer
"I suppose it's the way of hunters. We are very odd fellows." ~ Peter Hathaway Capstick