Booth weakest link

Hi, I am in the process of building a drum booth 12x10 feet. The entrance is a double glazed sliding door. The booth is floating on 1/2 inch neoprene and the walls and ceiling consist of 1/2 inch sheet of plasterboard, 3/4 inch ply,2x4 (airspace filled with rockwool) another 3/4" ply and 1/2" plasterboard. Given that the sliding door is the weakest link is there any point in adding more layers of plasterboard to the walls. On a different note, what are peoples thoughts on using insulation with only a cloth cover? Is it not a health hazzard? When I was stuffing the ceiling with rockwool it was floating all over the place. Thanks Stephen