Well, that makes sense. I've never done two servos in the wing center.

If the OP really wants to go with two, one on each wing panel, well, make sure the servo "box" is secure and attached somehow to the spar and not the balsa ribs and that the servo box is constructed of something that will securely hold the servo in place. I use a piece of 1/4" x 1/4" along the front and rear of the box where the servo screws go.

I've also run a piece of 1/2" x 1/4" on both sides of the servo from the spar to the leading edge then made the "box" out of that by two pieces of that 1/4 x 1/4 between the 1/2 x 1/4 to sort of form the box using the servo as a template as to where to glue in the cross pieces.

It's easy enough to do, you just have to use your head and make sure you're not shore'ing up to a piece of 1/16" balsa or some such thing. And, have the "box" the same distance from the center on both sides (don't ask)...

CGr.