Nice image to capture. I normally shoot my subjects like this in vertical also. This suggestion is just that and after seeing, I might change my mind too. But, I might would shoot this particular shot horizonal so I could get the complete shadow as well. It just gets cut in the right side of the image. That would also allow a little more control of the size at the bottom and top of the image. If I shot this vertical, I might would get a little closer so that the shadow leaves the image by exiting the bottom right corner of the picture.