ORIGINAL: stuk_at_work
Good points above that I forgot. The only thing you cannot do from behind the prop is start the engine. EVERYTHING ELSE should be done behind the prop, where it is safest. Don't forget to always wear eye protection too.
To add a comment to stuk_at_works post....I started building R/C and flying when I was ten years old. My instructor pounded in my head to do all adjustments from behind and it saved my fingers at one time. I was adjusting high speed on a Butterfly glider for a student pilot and couldnt figure out what that noise was, lol. Twas my nuckles getting "rejected" from the back side of the prop. Scared the crap out of me (was probably about 14 or 15 at the time) but I will always do any adjusting, etc. from behind. Very good advice.