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I have looked at nearly every photo online of a 750 rudder. It is almost equal chance that the nose skin will be under or over the rear skin. The assembly guide shows to put it under for drilling, but is never clear on if it is to be assembled that way. There is an extreme close-up photo of what I think is the corner. Simple aerodynamics suggests that it be over the rear skin so air don't catch it, and is what made me question it.
Anyway, the overwhelming majority of rudder pictures made at the factory workshop show it over the rear skin, so that's how I built it! I'm guessing it may not matter that much, or either a lot of folks have some rivets to drill out!
It took me about two hours to fix mine.