I understand the ceiling weight issue and that is one of my concerns. I do not understand the "hing in the middle". Can you explain in a different way?For ceiling material, I used barn siding. I have trusses on 4' centers, you are closer I am guessing. Light weight, but will span between and hold insulation, plus white reflects light. Plywood and OSB add structure, sheet rock is dead weight. I painted everything white for light reflection. If you hinge in the middle of your gable end, you can make your ceiling stringers accessible for long storage.