RE: Digital Servos and Battery Requirements
Assuming you are using normal heavy gage servo extensions and wire... the restriction is not in the wire. The problem is with the factory JR/Futaba connectors. Good factory connectors will work very well for a time. Wear from plugging and unplugging and charging through the switch and continuous charge/load rates higher than about 1.5 amps does the damage to the conectors. A worn connector can only take a little over 1 amp before heating up. Heat is caused by resistance. Keep in mind, if you are not using a Power Box you are putting the total load of all the servos through relatively small traces on the RX PC board.
FYI, high strand-count wire is better than low strand-count. Electrons travel on the wire surface and not through the core.
Also, if battery internal resistance (I.R.) is an issue, which is really is not any more with newer NiMH batteries, run two batteries of smaller capacity (thus equal to a big battery) on two switch harnesses. You will get all the current 'punch' you need and redundancy too. It also reduces current load through any given plug in your system by halving the current through it.
Use 5 cell batteries to give additional voltage to deal with voltage drops caused by long leads/multiple conections. Keep in mind that a 5 cell battery will not last as long as a 4 cell of equal capacity in a given airplane. Figure on about a 20% reduction in flight time/apparent capacity. Nothing is free... but bigger batteries are cheap.