Well you could do that. I wouldn't though. It won't turn out seamless, which is my biggest issue with hanging bead board horizontally. There will be a noticeable seam every 8'.
If you installed it the way it was intended to be installed you wouldn't notice the seams. Also with the lines going vertical it should make the room seem taller, which would be better if you have low head room. Hope this helps.-Gregg