FlatRat, is that the same length as the original rudder? I have a shovel nose Sanger ski hydro that rides/handles well at speed (low 10's at 106)...it's 11 1/4" below the bottom of the boat. Do you plan to go faster? I was told that a rudder with excessive length will act as a drag and pull the nose down at speed. I don't profess to know all, just what mine does.