Others. In the case of a group of business uses other than a shopping center on a lot held in single and separate ownership, a single freestanding sign, including individual signs identifying different establishments, may be erected on a common backing, provided that the total area of one side of the sign does not exceed 30 square feet and that any individual sign does not exceed four square feet. The structural backing for all such signs shall be uniform and no sign may extend, in any direction, beyond the outside edge of the backing. No portion of any such backing shall be less than five feet or more than 12 feet above the ground.