I have decided to use Dow 1 inch foam board to insulate the trailer.  The walls are all sealed with the foam board and then any gaps are finished off with "Great Stuff" expanding foam.  This keeps the foam board in place and ads approximatly a R=5.5 insulation factor.  Which does not seam like much, but I believe it will keep the 15000 BTU air conditioner from working over time.  And it will cut down on the outside noise transfer.

The ceiling will have a different setup.

I will be using the 1 inch Foam board PLUS a thermal radiant barrier that will make the overall insulation factor about R-22.  The barrier material has been used by us in Radiant floor heating systems and it has proved its performance.