some planes will pitch nose down with flap deployment--not all planes pitch up. Also, flaps shouldn't increase tip stall--they should prevent it by makins sure the root stalls before the tip does. However, ailerons on the outter most portion of the wing (as opposed to strip ailerons) very well can cause tip stall if setup for flaperons, because you will indeed be inducing a stall out on the tip of the wing only.