i had a Futaba Digital on the elivator of the Electric one and sometimes it would not wall (servo blow back) at the freestyle meet last year i did a verticle wall leaving the pull to about 15 foot and it just did a smooth pull out, just missed the ground then walled!! (Ali had his hands oner his eyes!)

i swaped it for a JR 8411 and its been perfect ever since

1 servo is only suitable if you use an 8411/8511 etc.

Malc is right about keeping all the weight in the middle but it still has to ballance, Servos are better than Lead