Our 5th wheel is a 1994 and at the time not many RV'ers had the axles flipped (truck beds were much lower then). I asked the factory to flip the axles after I discovered the tail dragged badly when turning onto our street (large dip). The factory flipped the axles and within a couple of trips I noticed the axles had shifted towards the passenger side by a couple of inches.
Back to the factory and they realigned everything and then welded cross bars from one side of the frame to the other. These were welded at the bottom of the I-beam frame to keep it from bending.
No problem since...