My plan is to install 1" rigid pink insulation between the 1" aluminum ribs of my trailer and seal any gaps with spray foam.
Then add 3" wide strips of 1/2" plywood to each rib with 1/2" rigid pink insulation between the strips sealed with aluminum foil tape.
Then attach the original 3/8" plywood sheets to the 1/2" ply wood strips.
That will give me 1 1/2" insulation (R 7.5) and a thermal break.
Just waiting for windows and slightly warmer weather.
Hope this helps.