Nobody in his right mind will be trying to start (or ride) a Slingshot when it's 10 below zero! But the Elio will have to start then, and I'd just as soon have some extra cranking power. I'd pay extra for a beefier battery if there were a place to put it.
An excellent point that I had not considered. I whine whenit gets to the 30's (F of course!) for a few days!