Kevin, this has been a hotly debated question for a long time. One of the better way, for my opinion, is to install a battery strickly for the servos and one battery for the receiver. This way, the receiver will get clean voltage with no spike from heavy current.
As for redundency, why would you need two receivers when only one was ever needed for the smaller airplane. It doesn't know the plane is bigger right???

Use 5 cells and if one cell goes bad, then normally it will short out and you will still have 4 cells to fly the airplane.

All the above, are my opnions only....