Here's the bottom view with the batteries mounted. I trimmed the mounting tabs off the backs of the line sensors, and mounted the battery case directly to the chassis, so that the battery case never touches the ground, even when Marauder is tilted backwards. Bigger...

I had to cut four holes in the case itself. This is where the bolt heads which from the vertical mounts that attach to the servos go. There are two #2 screws near the center that hold the battery case to the chassis. When the screws are screwed in all the way, the screw heads clear the batteries because the batteries are round. Bigger...

I cut a notch in the front scoop to allow the wires from the center sensor to be pushed a little bit further forward. They would normally be in the same position as the brass U channel seen in the picture. The brass U channel crosses the slot in the chassis (the slot is visible in the next picture). Bigger...

The nut seen here has been glued to the chassis (solder won't work since the chassis is made from aluminum). I used a cyanoacrylate glue (slower curing than crazy glue) to secure the nut. You need to be careful where the holes go because the servos touch the chassis. Bigger...

I got tired of juggling things while trying to screw the screw in, so I soldered the nut into the U channel. Much easier. Bigger...

Here you can see the battery case mounted in place. You can see the four screw heads that protrude into the bottom of the battery case, and you can see how close the battery case is to the front sensors. Bigger...