Rinse a 10-12 cup fluted tube pan or ring mold with cold water. Place gelatin in a large metal bowl. Add boiling water and stir until dissolved. Drain pineapple in a strainer set over a 2-4 cup liquid measure. Reserve pineapple. Add enough cold water to pineapple juice to bring liquid to 1 3/4 cups. Add to gelatin. Half-fill a large bowl with ice cubes and cold water. Set bowl with gelatin in ice bath and stir occasionally with a rubber spatula until mixture is as thick as unbeated egg whites. Remove bowl of gelatin and fold in remaining ingredients. Pour into mold. Refrigerate at least 4 hours until very firm or up to 3 days. (Check mold after 20-30 minutes. If marshmallows are concentrated on top, gently push down and stir in with rubber spatula). To Unmold: Dip mold up to rim in warm (not hot) water about 10 seconds. Invert serving plate over mold. Invert plate and mold together, shaking both gently from side to side to release gelatin.