Diablo RCU, I don't have a 22x8 Menz S yet so rather than wait on Gerhard. I ran the following
87oct,stihl 50:1,stock Taurus Pitts muffler I was tempted to not run any tests as this engine has about a quart thru it. But what better way to find out if it can take it.

22X8 NX (very nice prop) beefier than a Menz. 6975.
24X8 Menz S 6260
24X8 NX 6410
20X10 Zinger 3 blade with a thick front and back 6260
aluminum hub, total weight of blades and hubs added 12 oz.to the prop hub.
Now I realize these are not apples to apples because we use a stock Pitts muffler and not an exhaust deflector or using a 22X8 Menz S prop.I would guess at least a 200 rpm increase if I had one of those deflector gagets.
Hey how about swinging a three blade Zinger on your cantilever crank engine.
If I get a 22X8 Menz S I'll run it and post the numbers I get.