ORIGINAL: hllywdb
I've run a couple of Ace Pacers, almost identical to the Mach None, with a TD 051 on pressure and tried most of the props made. The plane flew the best with an APC 5.7X3. Might have made more power with a smaller prop, just didn't fly the plane well. Have to agree with CP on the rubber ducky 5X3 on the reed valve and sure starts. Unless the plane is a real dog, then an APC 5.5 X 2.5 will sometimes hoist the turd skyward with a surestart.
APC redid the 5.7-3 a few years ago to make the blades thinner and a little narrower. Looks more like one of the electric props they make than one of the plastic paint stirring sticks they make for 1/2A. Do you know if you had one of those props or the older style?