In case anyone is interested, I've an embedded video of HexPi with the better mousetrap servo tester controlling his front legs.
http://www.mikronauts.com/2014/06/11/hexpi-does-calisthenics/
It shows quite clearly how poorly some of the MG-995's behave - even with very filtered power.
I'll try to embed the video here, not sure if it will work (never tried to before) ... nope, did not work.