ORIGINAL: Flyboy Dave
....Hanes, BVD's, or Fruit of the Loom....

....do you like Fords, Chevy's, or Chryslers...
....what kind of fuel do you prefer....
...what's your favorite brand of engine....ect....
Hanes...
International Harvester....
15% Cool Power (20% oil)
O.S. (so far)
I usually try the MA, APC and wood Top Flite props in varying sizes on each engine/airframe combination. I've found that, for instance, my Advance 40 with an OS FS52S likes a 12-7 APC. This same engine on one of my SPAD DPS's prefers a 12-6 MA (standard one, not the K series). I'll be maidening[:-] this same engine on an Eindecker this weekend and I wouldn't be a bit surprised if it wants something different.
I think it boils down to each engine and airframe combination as to which is best. Try several and see what you like.
Disclaimer: The above results are from a purely un-scientific testing session and the results posted are based on the testing un-scientist's "gut" reaction. This test should carry a lot of weight in the RC community because of the testing un-scientist's enlarged gut.[X(] You're mileage may vary....
Have fun!