The answer to your question depends on the type of hinges you plan on using. If you're using a CA type hinge, you need to shape to a "V". If you want to use Robart hinge points (or similar), there is no problem with rounding your leading edge rather than tapering to a "V" shape. You just have to recess the actual pivot point of the hinge to the centerline of the radiused leading edge. If you want to round the leading edge, the trailing edge of the wing it buts up to should be concave to allow the aileron to recess into it. A radiused control surface looks much nicer (scale planes), but takes more work. If you decide to go that route, you can build up a surface on the trailing edge of the wing (top & bottom) either with some balsa sanded in concave shape to accept the rounded aileron, or another way would be to wrap the rounded aileron L.E. with waxed paper and temporarily mount it to the wing. Then mix up some epoxy with micro balloons and fill in the gap. Just make sure you sand it to allow enough travel up & down for your throws. (I hope that made sense!)

Pilgrim