Using a DA-100 I had to locate one of the 2 battery packs in the tail, and the other one uder the turtledeck in order to get it to balance properly with a pull-pull rudder.

With that in mind 2 servos with pushrods weigh about 5 oz. 1 Battery pack weighs 6 ounces, so putting two rudder servos in the tail should have about the same effect as moving a battery pack back. So you should be able to put one or two battery packs under the turtledeck (build a little platform) and two rudder servos in the tail and you should be very close. It might require a bit more tail weight or a lighter spinner to get exactly where you want.

Nobody can tell you exactly what to put where, but this will get you close.

TF