[OrrieG]

I would think twice about totally enclosing the space, especially if you live in humid environment. My truck which I purchased in AZ and has always been in high desert low humidity climate had the stock headline fail (took 30 years) from condensation from above. Its the same thing that rust out eyebrows, upper back windows and a pillars over time. A fabric liner will give the moisture an easy path, water vapor seeks the path of least resistance. It will also give you a way to take a look now and then to see if there are any problems.