Lined and Insulated Trailer roof.
Rationale; thermal insulation and sound deadening.
It is worth keeping heat out and at times worth keeping heat in, generally even temperatures are better than rapidly changing temperatures.†† The sound deadening is expected to reduce the stress of such things as hail falling on a thin metal roof, horses really dislike that.† Finally, the trailers are brighter as a result and there may be SOME reduction in the closed space sense that reluctant loaders get when entering a dark trailer.
A few words about tools and safety.
Working with sharp tools and power tools can be dangerous; wear eye protection.
Also gloves are a good idea when working with sheet metal, especially if your hands sweat and gripping the painted metal becomes a problem.† It is possible to get sliced quite badly if you lose control of a large panel.† Beware of drilling swarf and shards from scoring and bending sheet metal, clean up the work area frequently and if you use the floor as a work surface be very careful about kneeling on fine bits of metal, especially if you are wearing shorts.
I used a utility knife, cordless drill, 4ft aluminum straight edge, metal snips and a rivet gun.† A 110 volt drill might be a bit lighter; access to a shear would have been nice.† You could rent one, or borrow it from someone who does vinyl siding work.† I scored and bent the aluminum to break it, working to 1/16 th inch in most places.† This is very much like wall papering a ceiling in that you canít cut it all out and expect it to fit perfectly, you need to cut and fit as you go along.
The vent cut outs were marked with crayon and scored freehand, then torn out by starting at an edge and bending it a couple of times, once the tear starts it is easy to just run it around the curve.† Note they span the edges of 2 panels, so there is a U shaped opening on each panel, forming the oval shape when they are joined.† The flange is so wide that it is not necessary to cut out these openings very precisely.