What I did was built a fiberglass backing across the back of the gas tank area. It is contoured to the hump in the back. The rest of the enclosure is wood. It will take about half of the trunk space. The box front will be straight. Had planned on porting. Is it required? The sub will be facing upward, with a slight angle. Two tweeters also mounted on the box, for some highs. The amp JL 500/5 will be mounted on the floor of trunk concealed. The addition battery is a great idea. I can put it in one of the compartments in trunk. What Do you think of keeping the existing speaker and amp?