The complaint should include statements, records and other relevant information to support the requested apportionment modification. The aggrieved party may appear at the apportionment grievance hearing in person to present oral and written testimony, and may appear with or without an attorney or other representative. Authorization for appearances by counsel or other representation must be put in writing and bear a date within the same calendar year in which the complaint is filed. A quorum of the regulating district board will preside at the apportionment grievance hearing. The board may require an aggrieved party to submit additional evidence and, should the party willfully refuse to submit such evidence, or should the aggrieved party refuse to answer any material question, the aggrieved party will not be entitled to an apportionment modification or subsequent judicial review.