When I repaired the damaged rudder and fin on my H9 Corsair, (stick built flat surfaces) I sanded the trailing edge of the rudder down to a feather edge, and thinned the leading edge of the vertical fin a bit, then sheeted both (yeah, yeah, I know the corsair had a fabric covered rudder) with 1/32 balsa, and then sanded the LE to a smooth radius and re-feathered the trailing edge. Made for much stronger unit at minimal weight gain. I also extended the fin sheeting slightly past the rudder post, and rounded the leading edge of the rudder to produce a coved fin/rudder joint. Plan on doing the stab/elevators next.