The Rover5 doesn't have a top cover, but it has plastic posts that are designed to take self-tapping screws at each corner of the chassis. I purchased a plate of .090" T6061 aluminum at a hobby shop and laid the components. After cutting it to size with an angle grinder, and cleaning up the edges on a belt sander, I rounded the corners off. I then drilled a 3/4" hole to pass the wiring from the motors and battery up through the deck. This was drilled with a step bit, a safe way to drill nice clean holes in sheet metal.
I laid out and drilled holes to attach the plate to the rover chassis, as well as holes for standoffs to mount the motor controller board and IOIO. I drilled 2 1/4" holes to mount the two power switches, as well.
At this point, I ran out of time for the day. Next step is to mount the standoffs, mount the circuit boards, and test the motors.Right now I'm using 6xAA batteries in the holder that came with the Rover 5. Eventually I intend to replace that with a LiPoly pack, but it will work fine for testing.