Bring 1 cup water and sugar to boil in small saucepan, stirring until sugar dissolves. Reduce heat and simmer 5 minutes. Mix in lime peel; cool syrup. Combine pineapple juice, 2 cups gin, club soda, lime juice, and bitters in punch bowl. Mix in pineapple cubes and enough syrup to sweeten to taste. Add more gin, if desired. Add ice block to bowl.