The reason for four receivers is mainly redundancy. I'm not just using four receivers, I'm using them with FrSky RB-10 redundancy buses. The RB-10 has two battery inputs, which powers both receivers; so if one battery dies the other will continue powering both receivers. Or if one receiver dies, or has a brownout, the other will continue working maintaining control of your aircraft.
The reason for FOUR, is so I don't have to run signal lines - which can cause degradation - from the front to the back. So I have two receivers on an RB-10 in the tail for the elevators and rudder, and two receivers on another RB-10 in the wing for the ailerons and ESCs.
There still is a long run of FIVE power lines from the nose to the tail (right elevator, left elevator, rudder & two receivers), which is added weight, but the signal runs from the receivers in the tail are all relatively short. And by using 2S directly (and 12-14AWG wire), no UBEC, I minimize the voltage drop down the fuselage.
The reason for TWELVE 2S batteries is also redundancy and ensuring more than adequate power to all critical systems. Each servo (except for the ailerons*) is powered independently by two 2S batteries in parallel; that way if one pack dies the other can still power the servo, and if one servo dies it doesn't fry the others by being on the same circuit.
*The two aileron servos are powered together by two 2S packs in parallel, not two each (which would be four), because the aileron loads are FAR lower than rudder or elevator, and it is far more sustainable to lose one aileron and maintain safe flight control than it is to lose one elevator or the only rudder.
The weight of the twelve 2S packs really isn't a large percentage of the total weight, and in fact I NEEDED that weight in the nose to get the CG in a stable range.
So you end up with:
Wing RB-10: 2 batts
Tail RB-10: 2 batts
Ailerons: 2 batts
Right Elevator: 2 batts
Left Elevator: 2 batts
Rudder: 2 batts
That's twelve!
