The board shall determine the amount of premiums which the subscribers to the fund shall pay and shall fix the premiums for insurance in accordance with the nature of their business and of the various employments of their employes, and the probable risk of injury to their employes. They shall fix the premiums at such an amount as shall be adequate to enable them to pay all sums which may become due and payable to the employes of such subscribers, under the provisions of Article III of this act, under the provisions of the Longshore and Harbor Workers' Compensation Act (44 Stat. 1424, 33 U.S.C. § 901 et seq.) and under the provisions of the Federal Coal Mine Health and Safety Act of 1969 (Public Law 91-173, 30 U.S.C. § 801 et seq.); and, by reason of a subscriber's liability for all sums, such subscriber shall become legally obligated to pay any employe of his as damages because of bodily injury by accident or disease, including death at any time resulting therefrom, sustained by such employe arising out of and in the course of his employment, and to create and maintain the surplus provided in section 1509¹ and to provide an adequate reserve sufficient to carry all policies and claims to maturity. In fixing the premiums payable by any subscriber, the board may take into account the condition of the plant, workroom, shop, farm, mine, quarry, operation and all other property or premises of such subscriber, in respect to the safety of those employed therein, as shown by the report of any inspector appointed by the board or by the department. The board may, from time to time, change the amount of premiums payable by any of the subscribers as circumstances may require and the condition of the plant, workroom, shop, farm, mine, quarry, operation or other property or premises of such subscribers, in respect to the safety of their employes, may justify. The board may increase the premiums of any subscriber neglecting to provide safety devices required by law or disobeying the rules or regulations made by the board under section 1515.² The insurance of any subscriber shall not be effective until he shall have paid in full the premium so fixed and determined.