SOT: Is it safe to mount a gel cell battery in..., ... in the passenger compartment in a sedan race car? Options

[RoadGlue]

My friend bought my old Fiat sedan and has been taken it to a few DE's up at Thunderhill over the past year. Each time he's getting faster and so has the car. It's a '74 Fiat Sedan with a hopped up 1.8 TC, beefed up suspension and brakes and now a 1/2 cage that's been professionally built and welded in.

My question is whether or not his battery reallocation is safe. He's taken the front mounted battery and replaced it with a gel cell Optima and mounted it where the rear seat used to be. It has a single cross over mount and it's not mounted in a battery box.

The first pic below shows the mounted battery. The second shows the car before the installation, to give perspective on what you're looking at in the first shot. The ground cable utilizes the old seatbelt mount that you see in that second pic.

From what I gathered, it's OK to not have a gel cell battery in a box, but it can't be mounted in the cab. Plus, that mount doesn't look very strong, being that it's not sitting in a tray that limits side-side, forward back movement.

What do you think?