The arbitration board may proceed in the absence of any party who, after due notice, fails to appear or obtain a continuance. An award shall not be made without a hearing or based solely on the default of a party. The arbitration board shall (1) consider only those matters necessary for the resolution of the disputed issues, (2) have no authority to add to, subtract from, or alter the issues except as otherwise agreed to by the parties, and (3) not alter or modify any existing contract.