Of course, all of the above is discussion about concealed methods of carry. What if you don't have to keep the weapon concealed? (for whatever reason) The two most usable non-concealed options would be either a "tactical" thigh platform holster or a weapons mounting system that allowed you to carry the weapon right in the middle of your chest, canted for easier draw and presentation. The mistake most often made by folks (in my experience) using tactical drop-leg holster platforms is that they make sure the holster is centered on the outside center line of their thigh - along the outer seam of their pants. I don't understand this. It's a mistake I've certainly made in the past but if you think about it, it makes more sense to wear that holster just slightly forward on your thigh.
If you look at the provided picture you can see that the platform is centered on the pants seam as I described. My question is this: what if you moved that whole holster system about two inches forward? When we stand relaxed, our hand does NOT line up on our pants seam. That's where it is when we stand at the position of attention. When we stand relaxed our palms face in toward our leg and our hand is just forward of that outer centerline of our thigh. Why don't we position the holster so that the weapon's grip is right under our hand when we're standing relaxed? If you do this it also makes the holster / weapon a lot more accessible when you're sitting down.
For unconcealed carry that is probably the easiest to access and present, I prefer the center-chest mounted holster. This is a very aggressive appearing holster mount (obviously) but does grant ready access to the weapon and keeps it pointed in the general engagement direction. Using the platform shown (BLACKHAWK's STRIKE Mount for the SERPA holster) the weapon can be canted so that the butt is farther down (for easier access and draw), set horizontally or worn as shown.
So, although I've primarily discussed holster and weapon position options when sitting in a vehicle (of any kind), I'd encourage you to think about the various circumstances you find yourself in when you're carrying concealed (or not). The ultimate goal is to carry your weapon in a fashion that will give you the fastest and easiest access in the circumstances you most often encounter. That's just my two cents' worth though...