TL;DR article (and Musk) says the extra battery required to do this is dead weight 99% of the time. I guess the question is if Tesla stumbled on a feasible bat

TL;DR article (and Musk) says the extra battery required to do this is dead weight 99% of the time. I guess the question is if Tesla stumbled on a feasible battery technology that double energy per weight, would they choose to make an 800mi car that weighs the same, or a 400mi car with half the battery weight?