Any assessment association insuring property against fire, windstorm, cyclone, tornado, or other hazard which may be catastrophic, may participate with other insurers in financial plans or pools to protect the participants against excessive losses due to such catastrophes. For such purposes association funds may be deposited with or promised to trustees for the participants and loaned by such trustees to participants sustaining such excessive losses with provision for repayment over a reasonable period of years; Provided, that not more than twenty cents for each hundred dollars of insurance in force may be deposited or committed under such plan; and provided further, that participation in such plan must be approved by the Director of Insurance.