Well, I say Use Locktite and lockwashers. I have been using BLUE (medium strength) locktite and lockwashers now for 2 years on my DA engines. No problems getting them off when I need them off. It's added insurance that doesn't cost allot. It doesn't harm any component just use it sparingly.

My method for applying it is simple.

Run the bolt through the lockwasher, a thin steel washer, the thrust plate, the prop and then the spinner backplate. Now apply a drop of locktite and wipe off excess with your finger. Bolt on prop. DO NOT use a rag or towel on the threads this will remove to much compound. By using your finger you remove excess and leave just enough to do the job. This is a mount it and forget it method. I have never needed to retighten bolts nor have I ever had a prop come loose.

Having an impression in the wood is perfectly normal after removing the prop.