I am also flying my H9 Edge with a Moki 1.8 and the tail mounted servos. No added weight was required. Your Saito is somewhat lighter than the Moki with a Bisson muffler (Approx. 49 Oz.). My suggestion would be to mount your engine and all equipment except the elevator servo (servos), just tape or tack the tail feathers in place. Then put the plane on the balancer and decide where you want the servos. Do not permanently install the vertical and horizontal Stabs. till you decide as it is much simpler to make the modifications for tail mounted servos without the horizontal Stab. in place. Good luck with your Edge, I hope it flys as well as mine.
[8D][8D]. Oh yes, my rudder servo is pull-pull in the stock location.

RJ