For my N6.0 trailer, this spring I built a sail/gear box for a total cost of about $100 in materials. (The hinges, latches, and mounting brackets are the expensive items.) I gave the dolphin striker a couple inches of clearance and was still able to build a box that's 16 inches high (by 32" wide and 8.5 feet long).

To keep the heat down (which is not as much of a problem in Vermont as other places), I painted the box a glossy white.

I'm curious, though, about ventilation requirements. Assuming that the sails are put away dry and the temp inside stays cool, is there any reason for ventilating the box?

(I made the thing water-tight, using gaskets on the door. The bigger problem I've had in the past is from water coming in while on the highway in bad weather. My goal was to keep things dry while traveling.)