Divco, you have it mounted correctly (reading top to bottom.) Florida doesn't make a license plate that reads like the Minnesota plate posted above so this is the only way a vertical/perpendicular position can be interpreted. Vertical plates are worth the trouble. Slimmer profile and scratches less cars when you have to squeeze between them (parking, etc.)

With that being said, this is how I've had mine and yet I got pulled over for it 3 times in 2013. Now I just carry a print out of the statute with the specific mention highlighted. Apparently there are quite a few FL cops who are absolutely certain that this is illegal. Their reaction when given a a paper of the statute calling them wrong is entertaining though.