Fin Box Placement

I am in the process of building a 10’6" longboard. About how far forward would you place the back of the 10½" fin box from the tail? http://www.viser.net/~anthwind

I am in the process of building a 10’6" longboard. About how far > forward would you place the back of the 10½" fin box from the tail? 6" IS STANDARD.

…On my 10’4", I set it at 6.75"…