Smitty, If you have a 76'r I am sorry but I can't be of much help.
If you have a Bear Mag TD handle I might be of some help. Pics can be very helpful but string length depends on what handle you have (A, B, or C) and what length limbs you are using (1, 2, or 3's)
Once the blanks are filled in, and its a Mag riser, I can help.