I know alot of people who use cars for hunting and when they shoot a deer they lay a large tarp in the trunk and put the deer in then kinda pull the rest of the tarp over it to make a big bag so nothing leaks out and it works well. Seen it done many a times. And ive seen them strapped to the trunk lid as well which I think is better then the roof its a smaller surface area so theres less chance of denting then the roof and its not as high of a lift. Good luck this season!