I have re-drilled mine and your right the farther back you move the head the less support there is. However the Nacra 6.0 rudders I have are built quite strong. I have experimented with a few different rudder types in the Nacra castings and have ripped all of them off. Each time I put the old 6.0 rudders back on and go sailing.

Alum. rudder arm are very easy to adjust (bend) down once you find the rake your looking for.