The rounding looks good to me. The rounder they are, the easier it is to make the covering smooth over them so don't be afraid to sand on them more if you think it will look better to you.

As for the angle, a chiselled wingtip helps to provide a some dihedral effect. However in the case of the PT-40 the angle is very small, so the chisel effect is more for aesthetic purposes than any other reason. Kind of like why they make the tail in such a nice, fancy shape when simple a simple rectangular stab would work just as well.

Richard