RE: .30 or smaller 4 stroke engine?
Cool beans! Here is a picture of my dad and his "Playboy" when it was first built 25 years ago with an electric motor (Astro-05 I think).
My dad is 85 and has retired from flying but I modified it for an OS-26FS and it still flies today in his honor!
When we used to fly right until dark he used to say that it was a "nice sun-down ceremony", so I fly at dusk and think of my dad....
Good stuff!