If the fraternal benefit society is to be converted into a stock life insurer, the plan of conversion shall make reasonable provisions under which each adult certificate holder of the society shall have the preemptive right to subscribe to and purchase that proportion of the total authorized capital which the amount of his insurance bears to the society's total insurance in force at a date to be specified in such plan; except, that if more than 75 percent of the society's adult certificate holders are residents of this state, such preemptive right may, in the commissioner's discretion, under the plan be limited to such residents.