I've found that square edges on controls increase their effectivness...or at least make them "wilder" In a not so scentific test I built a Tidewater Pronto a long while back. They tell you to leave all edges square. Not knowing any different at the time, I followed the directions [img]i/expressions/face-icon-small-happy.gif[/img]. A flying buddy was building one too, but "knew better" and rounded everything.
Talk about 2 different planes.... Mine was very snappy, spun very well, etc; all around a great flying plane. My buddies on the other hand was sluggish. We matched control throws, ballance points, etc. His never flew as well as mine.
To this day, I leave the edges square on "snappy" models, and round them on more sedate planes.

Just my $0.02