Notwithstanding anything contained herein to the contrary it is specially understood and agreed that in the even of goods hereby insured or any part thereof being stored in the open-yard at the port of the landing named in the policy, this Company's liability for such goods shall be subject to F.P.A. only so long as they are so stored, provided, however, that the foregoing shall not apply in case of the Assured having given a previous notice of such storage to this Company and agreed to pay an additional premium required