How accessible is the inside of the back door? Im thinking of installing an air tank on the door but will need to drill holes, fit a bolt through it. If I had to put a nut on the bolt that is inside the door would it be possible to reach it with a wrench?

 

Once you remove the outside plastic vent, there's enough room to get your hand/fingers partially inside. Just be careful not to break the vents upper clips, ease it off slowly without too much force and you'll be good.