Pusher Prop for TH .75
Need recomendations for a pusher prop on a Tower Hobbies .75. It is on a Balsa USA Enforcer. I've read a few post that say 11x6 or a 11x7 pusher. The manual suggest a 12x6 or 13x6. Why are some using the 11x6 or 11x7 for the pusher? I am totally new to pusher props.