Every member of or subscriber to a rating organization shall adhere to the filings made on its behalf by the organization, except that any affected insurer may file with the commissioner a uniform percentage decrease or increase to be applied to the premiums produced by the rating system filed for a kind of insurance or for a class of insurance which is found by the commissioner to be a proper rating unit for the application of the uniform percentage decrease or increase or for a subdivision of a kind of insurance: (1) comprised of a group of manual classifications which is treated as a separate unit for rate making purposes, or (2) for which separate expense provisions are included in the filings of the rating organization. The deviation filing shall specify the basis for the modification and shall be accompanied by the data upon which the applicant relies. A copy of the filing and data shall be sent simultaneously to the rating organization. Any deviation developing a lower rate than filed by the rating organization may be utilized immediately by the member or subscriber developing the decrease. Any eventual return to the rate level as authorized for the rating organization, from which a lower deviation has been made, shall also be accomplished by submitting simultaneously to the insurance commissioner and the rating organization a copy of the filing and data.