Prepare cake mixes according to package directions. Bake in 4 round, 9-inch cake pans (you may do this in 2 batches if you only have 2 pans); cool thoroughly on a wire rack.
Prepare filling: Fold together sour cream and sugar. Stir in half the coconut (7 ounces, or 2 cups) to thicken the mixture for filling. Reserve remaining coconut to sprinkle over cake.
Measure out 1 cup of the sour cream mixture and set aside, refrigerated, to make the frosting.
Spread remaining filling between layers. Cover cake with plastic wrap and refrigerate 3 days to allow moisture to soak through cake.
To make frosting: Mix reserved filling with Cool Whip. Spread over cake. Sprinkle with coconut.Makes 12 Source: