Back when I still had the engine electric business, I had a customer that used 8-D batteries, (used in bulldozers, about 150 lbs apiece) and had them set up in so he could do welding on medical stuff.
He didn't use regular rod holders though. He said if you ever got into the connection (or became the connection) you would not have a chance to let go.
He said regular rod holders would arc back to his hands, so he used a big old thing that looked home made to me.
One day when I was there, he had about 12 batteries hooked together, (able to supply about 1,500 amps apiece for about half an hour) and he had an arc jump a 2-1/2 foot air gap and sustain it's self for about 25 seconds, with no sigh of weakening, until he got the power shut down.
I was impressed as all get out, but I just about wet my pants.
It was about a 1,000 Sq ft. room with about 10 foot ceilings, and the temperature went up noticeably in those 25 seconds. That arc was something!!
I don't get to see many DC arcs that last longer that 1000 micro seconds, and I damn sure never seen any, before or cense, that covered a 2-1/2 foot jump!!
I wouldn't be as concerned with footprint as I would be with the type of terminals that were used to connect to the batteries. The best we found were for heavy equipment, and were solid copper with a lead cadmium plating on them. I normally used the crimp type, and use a hammer crimper, then used silver bearing solder to seal the moisture out of the connections, then heat shrink tubing. Game over, you win.
It worked on over the road trucks that had exposed batteries to the road salt and crap.
I've seen people do it, so I know it can be done, but....
Be careful, the average car battery can sustain 750 to 1,000 amps for about half a minute, so there is real potential for electrocution here.
Later folks, Aaron.
When a fool and a wise man argue, Onlookers can't tell the difference...