I notice insulating the walls seems popular,but if you take an aluminum outer skin and insulate and ply the interior then FRP the plywood can no longer breath.
Warm inside,cold outside with no air movement will cause condensation and corrosion.
If you do not insulate you have a air gap between the plywood and outer skin which in itself is an insulation factor and still allows the wall to breath,also when installing the plywood leave a small gap between the pieces of plywood ends so it has room to expand and contract.
From the factory most roof's are insulated with loose fitted fiberglass matting and really has worked well through the years.
It is kinda late now but you could maybe get some 1 to 2 inch round soffit vents that are used in homes,Home Depot carries them and others,then using a size matching hole saw,find the roughly center of the wall beams (measure the rivets on the exterior) and a few inches above the floor line cut the hole through the FRP,plywood,and insulation and pop the vents in,then the walls can breath and dry out in between the sweating process,quick,cheap and easy.
There are probably other ways but this should be user friendly.
<message edited by RichardFla on Sun, 01/19/14 12:13 PM>