While on the farm or at my friends property we usually never leave the barn without at least one long barreled revolver and a rifle in some caliber. That said I usually have a rifle with me in most cases as well on my farm. If the rifle goes along, I usually have it rested against the center arm rest with the muzzle well outside the window. In your case this would be the butt rested on my right thigh, and muzzle out the window. I keep my left arm under the stock to keep it from battering around, which I could see if you were driving it might be an issue while shifting. For the most part the biggest issue is the barrel length. With my 25-06AI I have let it ride with the bolt back rounds in the mad, muzzle on the dash and butt of the stock on the seat. This works out fine as the barrel is 28" long so you don't just grab it up for a shot with it sitting muzzle on the floorboard. With my little Ruger Compact with the 16.5" barrel however, I just lay it on the arm rest. It is more akin to grabbing up a revolver anyway. I have to admit when I got it I really only got it for stalking in the river bottom where my longest shot might be 50yds at times. It however will easily reach out, and has, to 500 using store bought ammo.
If your simply sitting a feeder however I do not see an issue. It makes it quick and easy to raise up and acquire a hog or even a deer. (we mostly work on the hogs this way)
For two people, unless the back is open, well its just going to be step out behind the door sort of thing. The only other option is the passenger sitting away from the feeder, and stepping out in front or behind the vehicle to shoot, leaving the driver to do as above.
When my daughter was very young and also with my first grandson we hunted out of my Ramcharger in similar fashion. I normally parked it so that the passenger window faced the feeder so that we simply needed to roll down the window, pick the rifle up off the floor, poke it out, and slowly chamber a round. The nice thing about this was we put a bath towel across the top of the window and used it as an adjustable rest. That way the kids could raise it up or lower it to adjust it perfectly for however they were sitting in the seat. With an adult well you simply rest it on your arm or palm. If while we were out together I wanted to shoot, I eased out the driver side and usually rolled up the towel and rested across the hood. Thing about this is, you need to pay particular attention to the angle your shooting or you might put one through your hood and fender like my neighbor did while shooting at the biggest buck he had ever seen. A 180 class buck stepping out of the brush will effect even some seasoned hunters used to looking at them, but this fellow was accustomed to only seeing stuff in the 120's at best. That's whats neat about the river bottoms with good genes, you just never know what might happen to be there.
These are just how we worked through it. Yep there were times when we blew it as well, but for the most part slow and deliberate movements weren't noticed by deer and especially the hogs.
Hope this helps.