Unless you're putting a gas engine in there (NOT advisable) the model will balance fine with one elevator servo up in the radio compartment.

I have done two of these; one an ARF, the other a kit I built over ten years ago. The kit had an OS 120, the ARF (which I still have) totes a Laser 150 when it is in commission. The model wil handle a 30-35 ounce engine/muffler combo with no balance problems.

To be brutally frank, you're just causing yourself more work with the two elevator servo idea. Its simply not necessary. The single split pushrod supplied works fine, although it does need a bit of tweaking to eliminate any differential in the elevator halves. You would need to do the same thing with two servos.