191—20.8 (515A) Rate filings for crop-hail insurance. Rate filings for crop-hail insurance shall be submitted on or before March 15 of each calendar year. Each company may file one set of rates per policy plan per calendar year which shall remain in effect throughout the current crop year. In the absence of a new filing, rates on file from the previous year will remain in effect. Each filing shall be accompanied by a cover letter, synopsis sheet and supporting data which justifies the filed rate.