For war birds in the 25-30 lb range most of the war bird guys in this area, (altitude 5,000 feet) run one of the more common 22X8 props like a menz or zoar. I have found that I get better performance, especially speed, with an old standby prop from many years ago. I use a 20x8x14 Zinger, yes Zinger! It is comparable in speed to 20X10 carbon fiber props or 21X10 Bolly props, costs less and gives me the satisfaction of the look on the faces of guys who ask what I am using. The Zinger or TopFlight progressive pitch props were very popular , if not as sexy, in the 90's when gas engines became common. I think flyers went away from them when the 3D and IMAC planes became so popular but for war birds and sport flyers those fractional props work very well. As a rule of thumb the Zinger and TF props are thinner and more flexible so they depitch and unload in the air more. That means you should go up one size in pitch, in other words use a 22x10 instead of a 22x8. This only applies for war birds and sport planes. As I say, the difference between a Zenoah and a DA is like the difference between a Clydesdale and
a Thoroughbred. Use what you need for your application. For war birds the Clydesdale, for IMAC the Thoroughbred. Just remember the Clydesdale will still be pulling long after the Thoroughbred has been put out to pasture!
Larry