In truth your small Jr Ringmaster should have an OS 10 either an LA or FP. Other motors are the TT 10, Enya 09. If vintage motors are desired then the old Fox rocket 15 or a Torp 09, Cub 14, or any other LIGHT WEIGHT motor. Notice i didn't include the Cox TD09 which is probably the most powerful underrated 09 around and getting hard to get and plugs are expensive for it. Nor should you consider any modern 15 or 20 as you'll be grossly overpowered.
As to line length, built to reasonable light standards the plane flies fine on 52 foot .012 lines
Having flown them off and on for 50 years it is a fun type plane, never designed to do the pattern. I'm amazed that people think that it would. Power requirements were always modest for this plane. I probably would stay away from the Norvel 074 unless your able to really build light and I do mean LIGHT. With reasonable building technique and a light finish, please no monokote, it looks bad on these planes, you'll have a nice sport model.
dennis