You may want to fill all the holes with plates or just put .060 - .090 sheet bottom, sides, front and back. Also consider putting it over the top of the head cage. It will protect you from anything coming in on you during an incident.
Put a bar in 4 inches below your shoulders to mount your seat belts... you want those as short as possible.
Put on a firesuit, hans and helmet and climb in and out prior to placing the bars across the top for a dash.