I just checked the regs on the Wisconsin DNR web page and for ANY shelters you do NOT need to display any information as long as the shelter is occupied or in use. If you are on a border Lake that connects Wisconsin to Michigan, Minnesota or Iowa you MUST display the owner's name and address even if it is occupied, this includes Portables. Wisconsin law states that the letters must be Block Lettering and at least 1" square and be of contrasting colors. I would play it safe and have 2" letters for any lake in any state, this way you are covered.