In addition to locknuts and Loctite, it is also a good idea to use a prop hole reamer and make sure the prop to shaft fit is loose enough to be able to push the prop on the engine shaft without having to thread it on. That way, if the prop nut loosens from a kickback, the prop will be able to freewheel on the shaft and won't force the prop nut completely off of the shaft.
If you have to turn the prop to get it on the engine shaft, it will force even locknuts off of the shaft when the engine kicks back.