Agree with Jim. If those 15 or 19 are BR or TBR versions, then definitely the 41½" Flite Streak. TBRs in particular will produce power in abundance for the task. A Flite Streak Jnr. would simply be ridiculous. If PB 15/19, still not the Flite Streak Jnr as PB diesels tend to be heavy and slow, and the Jnr hasn't much wing area or section. In that case, you'd really be much better off with a "Peacemaker". As I understand it, the original Jnr was designed to fly with '50's Fox .15 'power' or equivalent. Output of an O.S. .10LA today would cruel it, and is about perfect for either the Flite Streak Jnr or slightly smaller Mini-Peacemaker.