When I was into RC car racing we would do cap matching to build our NiCad battery packs all of the time. I can't imagine it would be that much different to cap match NiMH.

I'm guessing that, as mentioned earlier, the BCMs & ECMs might not be able to harness the extra capacity due to their programming.

"Speed doesn't have anything to do with mileage. My truck has an overdrive gear for a reason." - Credited to an unnamed Freeper reguarding changing the speed limit back to 55MPH.