So I got the Evo2 16-cell installed and tested. Bottom line is it works great, just as ChipsWithDips said it would. Install/test info here:
wstar's Journal . It's really a much nicer solution than relocating a heavier battery. As with all minimal battery solutions, I wouldn't recommend it (or at least, would recommend caution) on a regular street car where you might run the stereo or the lights for a while with the engine off. Especially with this battery, since the manual specifically states that if you drain an LiFePo4 battery below a certain critical voltage the (rather expensive!) battery is basically toast and can't be recharged.