In a medium bowl, slice bananas and sprinkle with lemon juice to keep them from turning black. In a 2 quart casserole dish layer the vanilla wafers and bananas. (I use 10 of the wafers to go around the side of the bowl just because I think it is pretty this way). In a saucepan on top of the stove with a whisk mix together the sugar, salt, flour, egg yolks, regular and evaporated milk. Cook on medium heat, stirring continuously with whisk, about 7 or 8 minutes until thickens. (It will burn very easily so be sure to stir) Remove from stove and stir in vanilla flavoring. Pour over wafers and bananas.