I just purchased a GP 1/4 scale Spacewalker. The recommendation is to install a second servo for the elevator. Since the original servo tray is full where would I mount the additional servo? Would I setup the throttle servo infront of the existing tray?

I set three across with the rudder in the middle (as a pull pull) and the elevator servos on either side. Used a reversing wye so that both pushrods were on the outboaard side of the servo arms and crossed them inside the fuse so that it was a straight shot to the elevator horns[8D]

I used a small HA 81 for engine and mounted just behind the former where the front of the wing slides into

Back when I had my Spacewalker (God rest it's soul...may it's battery fry in hell! Oh wait, that was just my early "watch the battery charge" lesson)...I just expanded the servo tray to accomodate four servos with a dremel. As I recall there was plenty of wood in that tray to work with.

If you want to do the extra work and mods for a second elevator servo, go for it, but it's not really necessary on this plane. I have a single high torque servo in mine and it works just fine. Another guy in our club has one set-up with a single also, no problems.

I mounted two low-profile servos for the elevator under the horizontal stab, with short linkages to the elevator halves. This is done partly to offset the heavier gas engine up front. I don't recommend the servos in the tail if you are using a lighter glow engine, as this plane tends to build tail heavy. I just like dual servos and short linkages better than single servo and long pushrods in general.