You can vent, keep air moving by the inner hull
interface, or insulate, don't let air of a different temperature reach the cold hull
. I like the plan that prevents air of a different temperature comming in contact with the inner hull. You can lay a foam sheet of the Qwens-Corning pink insulation sheets
sold as 4'x8' panels
under your bed
and against the hull.
I must admit that my 43 years of sleeping in the V-berth is not harsh. I spend the winters south and the summers north, but I still choose the "insulate" plan over the "ventilate" pln!