Public officers and governing boards having control of public funds on deposit in any such bank are authorized to join in any plan approved as provided in section 26-1026, Idaho Code, if, in the judgment of such officers or boards, the plan is for the best interest of all persons concerned, but no such agreement shall release any surety on any bond securing public deposits or public funds, or waive any security held for any preference given to such public funds under any law of this state, or relieve any officer, or the sureties of his official bond, of the liability, if any, for such deposit, and the time for the repayment of public funds shall in no event be extended for a longer period than six (6) months from the date of said certificate of the director of the department of finance.