Add rice and margarine to pot of 2 1/2 cups boiling water. Cover and simmer for 20 minutes. Combine cooked rice, sour cream, mayonnaise, onions, salt and pepper and 4 slices of bacon, crumbled. Mix well and place in 9 x 13 casserole dish sprayed with non-stick cooking spray. Sprinkle remaining crumbled bacon on top. Cover and bake at 350* for 30-35 minutes.