A knife edge trailing edge is a requirement for real high speeds... pylon racers, slope racers, etc.
Nice but not mandatory for something like a pattern plane.
The shape makes no difference on the ordinary sport model.
As long as there's not too much mass hanging off the hinges, that is.
Fun flies with blunt surfaces NEED a tight control system to keep the surfaces on the airplane.
Even tapering won't do much good if the surface is floppy due to loose hinges, pushrod connection too close to the surface at the horn, a thin/whippy pushrod, overly heavy wood for the surface...