RE: TT 39 Heli Engine
Your factory piston ring might just suck and should be replaced with a Frank Bowman ring. Not all rings are created equal. Some imported rings take forever and eternity to break in and seat, if they ever do. Maybe TT used a crappy ring in that engine?
Did you get it used or NIB?
Also, could you post a picture of the inside of the liner where you say it's out of round?