(1) A crop hail insurer proposing to use rates or advisory final average loss costs, based upon the rates or advisory final average loss costs filed by the national crop insurance services but which deviate from those rates or advisory final average loss costs in any aspect, shall first file the proposed rates or advisory final average loss costs with the commissioner of insurance for his approval.

(2) An insurer shall include with rates filed pursuant to subsection (1) of this rule, cumulative crop hail statistics indicating the insurer's expense loading substantiating the proposed rate deviation.

(3) Proposed rates subject to subsection (1) of this rule shall be filed on or before March 15 of each year.