You should look in the val file under ShipWake for the values
StartParameters
--LeftVertex
----StartPosition the 8 bytes that follow the null termination are the x/z coordinates
--RightVertex
----StartPosition the 8 bytes that follow the null termination are the x/z coordinates
One controls the origin of the wake on the left and the other on the right
For the length I think it's
FadeOutSpeed
Ref