I'd suggest to start thinking about the roof mounting now. A few times moving that module around and packing it up will have it screwed to the roof, quickly. You also will gain the advantage of having the panel charge the batteries while underway. For winter storage, configure the mounts so you can swing one edge of the module up and leave the other connected. A simple pair of struts under the high edge will allow for panel tilting in the Winter. No more schlepping panel, no more battery care in storage, no anxiety about panel moving to another guy's house.