Nope, a left hand thread would make things worse. The drag of the prop tightens the prop nut. On a left hand thread, it would try to loosen it. The starter will try to spin the prop off, especially if the engine is over primed, but once it starts it is being tightened. This is all academic though because props don't loosen in flight or when running. The become loose when the engine suddenly stops.

Four stroke engines are more prone to a back fire and spitting the prop. They almost all have a lock nut arangement, and not just a second nut screwed on top of the first, but a cone/collet arangement so the lock nut clamps tighter on the shaft as it is tightening. This doesn't prevent the prop coming loose on a back fire, but it does keep things together. The only engine I've ever had a prop come completely off of was a O.S. 40 two stroke that was running to lean and when it got warmed up, it siezed and the prop came roaring off.

There is nothing to keep you from using a four stroke prop washer, nut, jam nut on you two stroke engines, assuming you have enough thread length. The O.S. and Magnum engines use 1/4-28 and 5/16-24. Saito has the metric sizes if that is the thread size you use.

Don

A better fix than sandpaper is open mesh sandcloth for plumbing. It bites into the plastic on both sides and will not move once you've tightened it.