I flew a Junior Flite Streak with TD 09, 10% Sig Champion 20% oil half castor, half synthetic, Cox grey 7 x 3.5 prop, 57 ft 12thou lines. On 55 ft lines I was getting 3.8 sec laps, pretty darn fast for an old man to fly stunt with. With the 57's it was just over 4 sec laps and I could fly it OK. I think a Medallion 09 would be fine, maybe better, for a Junior Flite Streak on shorter lines. No way I would put one on a Baby Flite Streak.