I use Markins' plates on ALL my cameras, they are very nicely machined.
In my case, when I mount a camera to support, it is either onto a monopod tilt-swivel or a gimbal. To mount on these I need forward orientation which Markins' unique bi-directional plates provide. The D800 bi-directional plate is the nicest one yet, with a beautiful curved outline exactly matching the curves at the base of the D800 body. These bi-directional plates are not, as far as I am aware, available in an L-design, but I have my monopod tilt-swivel which can be mounted to my gimbal to allow portrait orientation shooting. Because I use a gimbal, I don't use a ballhead (aside from I have one for my ground pod for occasional use).