RE: Speed controller advice
You are dealing with 2 problems here. The BECs in most controllers are rated at 5V and 1A for the receiver and all servos. Larger servos draw more current than smaller ones. If you can use 4 small servos that do not exceed the 1A limit everything will work fine. The voltage regulator in the BEC pritects itself by not allowing more than 1A to be drawn from the circuit. The other problem, which is far more serious, is the difference between the battery voltage and the BECs 5V output. The higher the battery input voltage the hotter the BEC gets. If the BEC gets too hot, it will shut down and your receiver and batteries will not operate. If you can afford the weight use a receiver battery and avoid the BEC.