Here's my setup for the Pie Servo.
It's not fancy but it gets the job done.
I used a Hitec MG85 servo and a 4-40 linkage to the hinges. The hinges I added a small threaded rod from hinge to hinge and this gave me something to attach the rod too.
The only thing I want to change is the treaded rod, I want to used some smooth rod so the arm does'nt grab the threads as it moves. Also the rod in the hinges has to be free floating or it will bind up the hinges as the move. As you can see in the video, The servo has more than enough power to open/close the pie panel.