Probably going to go flat.
Yea I also have been thinking about a liner material like Al's, Raptor, Monsta, etc. The only thing steering me away is the huge PITA it would be to reverse it in the future.
I'm leaning towards one of the GCI (Gillespie Coatings Inc.) colors. You have to buy them through a company called Rapco... Link below
Rapco Paint Descriptions
Will likely go with an Olive Drab since everyone and their mother are painting 80's tan these days. One of these 3 color codes would work... 319, 34086, or 34052