The way the pyramid brace is set up, you are ahead of the axle to start with. Moving it back 6" would put it basically right over the axle -shouldn't be an issue. And no, unlike a slider hitch, if you wanted to swing it around, you would have to completely disconnect and set up your 5th wheel to stand on its own, then take off that gooseneck adaptor, remove the hex bolts, 1.5" bolts, then re-install the box, re-torque it, etc. NOT a "quick thing" to do. Once it is on the kingpin, you will want to leave it there.
that is about the only part of the Andersen system that takes any real time at all (and I'm still only talking about maybe 10 minutes) but their instructions suggest you mount it permanently reversed for short-box trucks.
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