A radius is more aerodynamic than a square edge so, if they aren't rounded, I would.
Are you a total beginner, meaning no experience flying or building? If so, I wouldn't try to fly that Cub as a first plane. I would finish it and hang it from the ceiling or put it on a shelf as Cubs are not a good plane to learn on. I would find a trainer or a trainer kit and learn to fly using that instead.