How common a practice is this?.

[Licensed to kill]

I saw a model A for sale the other day and in the description it stated, "has 8 volt battery to spin it over faster". I never thought of that before, but, then again, I'm quite content with the 6V. I doubt that an 8V battery would cause any issues with the rest of the systems, IE lights, horn, generator, ignition system ETC. Anyone else running an 8V battery in their 6V system?. I'm not interested in doing it, just interested in the concept.