I'm not familiar with your boat in particular, but I assume the reason you asked is due to limited space for insulation around your box? If so, some of the best thin insulation is used in the hot rod industry to place under the carpet/floorboards to keep heat/cold from migrating into the cabin. there's several foil backed insulation packages that are in the 1/2" range, and if your really cramped for space (or in addition to the foil backed stuff) there's a product called Lizard Skin that was originally invented for use in the space industry. it's a spray on product about the consistency of truck bed-liner. the Lizard skin is pretty amazing stuff and might warrant your doing some research on that. If you look into Lizard skin, make sure your looking at the heat barrier stuff, as they also make one for sound insulation.
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