Drain Pineapple, Reserving 1 Cup Juice And Six Pineapple Slices (Save Remaining Juice And Pineapple For Another Use). In A Large Resealable Plastic Bag, Combine The Brown Sugar, Ground Mustard, Garlic Salt, Pepper And Reserved Pineapple Juice; Add Chicken. Seal Bag And Turn To Coat; Refrigerate For At Least 2 Hours, Turning Occasionally. In A Small Bowl, Combine The Mayonnaise, Dijon Mustard And Dill. Refrigerate Until Serving. Drain And Discard Marinade. Grill The Chicken, Covered, Over Medium Heat For 5-6 Minutes On Each Side Or Until Juices Run Clear. Grill Pineapple Slices For 1 Minute On Each Side. Spread Mayonnaise Mixture On Rolls. Top With Lettuce If Desired, Chicken And Pineapple.