I did my Savage with a second servo..is it good or not depends on what you would like to do..It is kinda cool for a minute doing cab walks and super tight turns. I had a switch to turn the rear steer servo off/with/opposite the fronts on my controller
Any way it is very unstable at speed and I had to tune all but a very little and at a slower servo speed..and it worked ok.
Now I run the steer arm locked but the servo saver still allows the tires to move. They give just a little on hard turn in. I may get back to it again ...
Here is more than too much other info..
"cabbie" made a single servo linkage one that was great