Mix graham cracker crumbs, 1/4 cup brown sugar and margarine. Press in bottom and up sides of a 10-inch pie plate. Bake in 350 F oven 8 to 10 minutes. Let cool.
In a medium saucepan, sprinkle gelatin over pineapple juice. Let stand to soften. Add egg yolks and remaining sugar and beat well. Cook, stirring until gelatin and sugar are dissolved. Cool slightly. Puree bananas and rum in blender. Add to gelatin mixture with nutmeg and salt. Chill until mixture mounds on a spoon. Beat egg whites until stiff peaks form. Fold into banana mixture with whipped cream. Pour into pie shell and chill until firm. Garnish with additional whipped cream and banana if desired.