Did you buy a 19-1, 19-6 or a 22-2. Only the 22-2 was a flatback up to the end of 71`. The 19-1, 19-6 was a little unique to itself with a slight modified V and a small stepped "pad" until 71`. For the 72` model year the 19-6 and 22-2`s were 12 degree V`s.