You could try more rear toe, too. Then again, with much of an adjustment there, especially if the toe is gained at the arm mounts, I wonder if the springs would no longer be balanced.
In regards to nitro/gas cars, I'd use the average or middle fuel level. The worst case scenario is that your imbalance is off by half the weight of the tank. If you tune to either full or empty, the worst scenario is that the weight of the entire tank is the amount you are off. Location of tank will affect things too. I have only ever run electric. Keep in mind that on a real car, if the vehicle weighs 2500 lbs and a tank of gas is 18 gallons, that's only a little over 100 lbs difference full to empty which is only a few percent.
Yeah, but what about all the juice we put into the batteries when we charge them?
I agree. This thread is great.