Side and rear yard regulations for accessory structures and uses. Subject to the setback requirements set forth in Paragraph F(5) above, parking areas, wherever located, and other detached accessory structures and uses, when located within the rear 20% of the lot, shall not be required to maintain an interior side or rear yard or setback in excess of five feet unless the lot abuts property used or zoned for residential purposes, in which case a twenty-five-foot setback shall be maintained; provided, however, that this regulation shall not apply to antennas and antenna support structures; and provided further, however, that no accessory structure or use, or combination of such structures or uses, located within an otherwise required side or rear yard pursuant to this paragraph shall occupy more than 30% of such required yard.