Melt margarine and 1/2 cup Sugar Twin. Roll biscuit bits into cinnamon mix and place in greased tube pan, one layer at a time. Pour melted margarine mixture over each layer. Use raisins and nuts as you choose. Bake at 325 degrees F for 30 to 40 minutes. Invert while hot. Return to oven on plate with oven off for 30 to 60 minutes.