I've done this on several boats, it's not too bad a project and the results are very satisfying.
You definitely want to allow for ventilation, and epoxying vertical furring strips is one way to go. You will likely have to kerf cut wood strips so that they will conform to the hull curvature unless you use foam for that purpose (it can be glassed over to provide a surface for a screw to grab)
In my current boat (single skin hull) I put wooden furring strips as described, about 3/4 inch thick, then glued 1/4 inch foam insulation to the hull to discourage condensation. The remaining 1/2 inch gap provides air circulation. I then used two inch battens to plank the area, leaving a small 1/8 or so gap.
I would not use tongue and groove because I think you need the circulation all around. The toughest part is getting it to lay cleanly as you adapt to the compound curves - some twist will be required and some pieces simply won't want to go in easily. Another tricky bit is deciding what line your planking should follow - this is mostly an aesthetic decision - do you want to follow the shear line, or the top of the berth, or find some middle ground? There will be tapering required at the ends of each section.
But by all means give it a go - looks WAY better than carpet or any other such liner.