Hinge Center Line
If you follow the plans, the hinge center line is farther out on the bottom. It was explained to me that this allows the rudder to swing out at the bottom increasing rudder effectiveness. This works with two hinge points, but this part of the design was not carried through on other models because it does not work with three hinge points as they must be in line.
If you look at the plans closely, you will see the skin is trimmed on the top more than the bottom and the rudder is not parallel to the HS.
I dont think there is enough offset to make a significant difference, but Van was a purist and it shows in the design of the 3.
I think most make the rudder parallel to the HS and dont follow the plans strictly here.
(by the way, the dimmension for the bottom hinge bracket hole is not shown. You have to add up the material dimmensions and do the math to fiind it, all part of the fun of building a 3)