IMHO it is better NOT to use anything on the screws. I use them as indicators for potentially dangerous situations regarding vibrations or imbalance in flights loads. That is to say that I recheck all the screws every 30 flights or so. If they all require a quarter turn, them all is well but if only one is very loose... I will further investigate. That was the initial idea anyhow. As it turned out, I had to retighten a minute amount after the first 10 flights or so and they have stayed OK after more than 100 flights so far. I will keep that check however, not only because it is a good practice but it also contributes to your good safe feeling with your machine. Do not forget the motor screws, they are the one than are more suceptible to loosen up (and they do...)