HI RICCARDO17! I can't see the pictures, but are the elevator halves controlled by a split push rod, or seperate servos? You need to find perfectly matching servos if you are using 2. If you have any binding in the hinges, or a weakly built control surface , you will have a problem. But in practice, if everything is sound and hooked up correctly you might not win any pattern contests, but slight deviations in control deflection at typical sport flyer speed shouldn't cause a problem. If you grab the elevator and push against the push rod,[most designs are push for down, pull for up] the elevators shouldn't move. Same goes when you pull on them. Don't do this test to the point of damaging the servos, but you want to be sure that this question is answered in YOUR head before you fly.