I have an Spirit 100 electric conversion. The gearbox is a Promaxx with a 5mm shaft and I'm using AeroNaut prop adapter, yoke, and spinner with a 17x9 folding prop. I'm having a lot of trouble with the set screws coming loose. I've replaced the set screws with no improvement. The set screws also seem to dig a tiny ring notch into the shaft and also seem to produce a slight ridge next to notch, which makes the adapter very difficult to remove.

Are there any good techniques for securing the prop adapter in a sure and solid way? This arrangement just seems inadequate for the equipment. Large prop and strong motor (Aveox 2739-1.5). I can "clean up" the gearbox shaft pretty easily by smoothing out the ridges, but does it need replacement? Is it a good idea to file down a flat spot (or 2 - there are 2 set screws)? How about drilling indents into the shaft for accepting the set screws?