My two cents worth: Back to snownskate"s original question:
I have a ancient Sig Quick-built Mustang approximately the same size as the Top Flite Mustang. I weigh about 9 lbs with an os 91 (pre surpass) 4 stroke swinging a 4blade Zinger hub with 16-8 prop blades cut down to a 12 dia. This gives a paddle blade appearance but certainly not scale. The plane flies quite well (big loops from level flight) but no unlimited vertical rolls like some I see. I have put a 14-7 2 blade prop on and the "performance" is very much faster (vertical rolls out of sight). However it doesn't look "scale" or sound "scale" to my likes. Similar results with the Byron Corsair with Sachs 4.2 and 3 blade prop. At our local Giant scale fly in I used to fly "combat" with another Byron Corsair with same engine but the 2 blade prop. His engine turned way faster and his plane was far faster, but to my tastes it wasn't as "scale" flight. Many of the spectators also say my planes look "smoother" in flight. Others say "looks like it needs more power". Boils down to how does the pilot want his airplane to fly!