Ken, I think your intuition and some of the advice you're getting are letting you down. A little calculation could bring some insight. Here are some numbers for an airplane the size of Paul's and the weight of yours. Guys, check my assumptions and ciphering:
Assume power losses from ESC, motor, battery and wiring = 20%
Assume prop efficiency = 70%
Average battery voltage = 22.8
Battery usage for 6-minute flight = 2 Amp-hours
Average power leaving the battery = 456 W
Average power dissipated by ESC, motor, battery and wiring = 91.2 W
Average power going to the prop = 364.8 W
IMHO the biggest culprits in wire loss are the connectors.
Maybe so, but if 10% of the power went to a connector, it would be on fire. You can measure the power loss. Put a voltmeter across the connector and an ammeter in series with it. Multiply the readings.
As far as wire length goes, the only critical wiring is between motor and ESC and between ESC and battery. These wires are normally heavy for a reason. Very high current does create a voltage drop, which will rob the motor of power if wires are too long. Remember also that motor power is adjustable by increasing the pulse width to the ESC, That could compensate for wire losses, and all would be back to normal.
If absolutely necessary, wires can be extended if wire size is next larger size than originally provided. Very heavy flexible wires are sold just for this purpose.
Mind you, this is coming from a EE. I don't believe it. 20-gauge wire has a resistance of .01 ohm per foot. At 20 amps, that's 4 watts / foot. We aren't using fat wire to minimize resistance losses. There may be some Eli-the-Ice-Man reason for fat wire. Tim can explain it. I use fat wire because I need the nose weight anyhow. If I didn't, I'd look into the reason for it.
The amount that comes out of the battery is significantly influenced by the prop being used. Be aware!
Be aware indeed. Propeller efficiency, which you can calculate if you want to, and which you can do something about if you use one of the available prop design programs, can vary a lot: probably from 50% to 80%. I assumed a prop efficiency of 70%. I use 2,000 milliamp-hours of battery per flight. If my prop were 50% efficient, I'd use all 2,800. Prop power dissipation is a couple of orders of magnitude more important than wire dissipation.
My goal in all of this is to design a light ship that has the bulk of it's heavy items at or near the CG then be able to add/remove ballast to achieve the optimum weight for current conditions. Similar to what I would do if I were flying sailplanes.
There is some discretion about where to put some of the masses in electric stunters. The battery is the big one. However, the minimum moment of inertia (the barbell effect) is with all that stuff at the same place. This is contrary to folks's intuition, and I've posted a calculator to demonstrate how it works. The optimal mass distribution is with the battery, ESC, TUT, BICAS, wire, and switches close together and wherever they need to be to get the CG to come out right, which is way forward of where the IC airplane's CG comes out with or without fuel.
That said, there may be an aerodynamic reason for having the motor farther forward than it would be for purely mass reasons, and moment of inertia is not that big a deal. It's not worth having a short nose with a bunch of ballast in it as I've done.
I don't think the sailplane analogy holds. The design task, hence the reason for ballast in either case, is different. I can imagine no need for ballast in a stunt plane with a control system having sufficient leverage over hinge moment.