Ben, probably one of the things that makes pull pull rudder installations easy is that the fuselage is usually symmetrical from side to side so the installation is a mirror image of components. Plus most of the time only one control surface is involved.
Elevators usually are split plus the top and bottom cable exits most likely will be in different locations fore and aft due to asymmetry of the fuselage top to bottom.
These are not show stoppers in the least but I think that non scale and semiscale flyers find the scattering of servos easier than the routing of control cables.
I have large scale planes flying with servos direct, pushrod elevators, and cable controlled elevators, depending on the scale requirements. Non out perform the other. In the end probably design and mechanical skills probably are the deciding factors.
ORIGINAL: Ben Lanterman
Giant scale folks make an effort to make the rudder pull-pull with 4 servos ganged up for rudder. Then for control "goodness" they go to an aft mounted servo or two servos on each stabilizer half and a short pushrod to the elevator.
Why the difference? Certainly a tight pull-pull system is just as tight as a direct servo connection. Or the reverse, if direct is so good why not use it on the rudder?
Another question. Why use a pull-pull when a big diameter carbon fiber tube push rod would be rigid and let you put the servos up in the equipment bay?
Granted dual elevator servos per elevator half gives some reduncy in failure analysis.