I had tried many a prop on those 3 Mustangs.
The first 2 were take apart, and every part was interchangeable. The first used Saito 56. The second a Saito 72. The third was a one piece configuration to see how light it could be made. It was 62 ounces, and with a 72 was a very good flier. It also sported a Saito 82. That motor was a monster, but had more vibration issues than the 72. Likely why they never went into full production.
The props tried were as follows. The first was a Yatchenko 13*5 wood prop. I liked it well enough to have Brian Eather make carbon versions of it. They worked well, but the mass of that club was a bit much. I then tried various diameters of the Bolly 3 blade series. 13.5 diameter down to 12.0 diameter. Pitch ranged from 4 to 6. I settled on the 13.0 diameter with 5 inch pitch..
The plane flew better with pitch lower than 5, but the motors did not like to Rev that high. Fuel was YS 20-20. By far, that was the best fuel for those motors.
One thing to be aware if is the variability of the Saito motor builds. I had one that was clearly better, so I set out to find out why. It seems that every one was slightly different. The cam lobe shape was not consistent nor was the assembly. Some were off a tooth on the cam timing as well.
Have fun playing with these.