Damien, Rookie editor here. I had a wonderful senior girl ask to do the following pose while I had my narrow backdrop on. I have followed the extending background instructions you posted, but I feel I am losing shadows and making her look like she can hover. I tried hopelessly to add a gradient adjustment layer. I will attach the adjusted original. I use PSE and this image was shot as a jpeg (I forgot to switch my camera over after) shooting video).
Sincerely, Hopeless Editor