Grounds in appeal: appellants need leave to raise unpleaded grounds, and parties must get an opportunity to be heard before decisions rest on new grounds. Appellate practice restricts appellants from urging or relying on grounds not specified in the memorandum of appeal unless they obtain leave of the Tribunal; the Tribunal may consider additional grounds when deciding an appeal but shall not rest its decision on any such grounds unless the affected party has had a sufficient opportunity of being heard on them.