On full size aircraft flaps are used for landing and taking off . They increase lift and drag so at the same time that they increase the lift of the wing they allow you to slow down . When first deployed your aircraft will often pitch up depending on your speed . So to prevent this down elevator is mixed in with your flaps . Even on full sized aircraft when flaps are deployed you trim in down elevator. You need to set this by trial and error. It dosen't take a lot . One other thing I like to do is slow my flap servo down .Not all radios can do this . It makes the pitching up a lot easier to manage untill you get the mix set properly .Flaps are great for slowing your aircraft for landing and if it looks like you can add them I would not hesitate . If you have them and don't like them you don't need to use them . I think however once you get used to them you will be very happy to have them .