Dell's mount will be the one I will model against... when I finally work on my dual system... next year
If your heart is to mount together... there are posts of people that just modified that area to be stronger.
By making up a battery tray that is triangulated and bolted to the frame of the truck.
That will remove the majority of the stresses on the fender from the two batteries.
If I find that link - I will post it up for ya.