In a large saucepan, mix sugar, flour and salt. Whisk in milk. Cook and stir over medium heat until thickened and bubbly. Reduce heat to low; cook and stir 2 minutes longer. Remove from heat., In a small bowl, whisk eggs. Whisk a small amount of hot mixture into eggs; return all to pan, whisking constantly. Bring to a gentle boil; cook and stir 2 minutes. Remove from heat. Stir in vanilla. Cool 15 minutes, stirring occasionally., In an ungreased 8-in. square baking dish, layer 25 vanilla wafers, half of the banana slices and half of the pudding. Repeat layers., Press plastic wrap onto surface of pudding. Refrigerate 4 hours or overnight. Just before serving, remove wrap; crush remaining wafers and sprinkle over top.