In addition to the information already posted, note that 4WD is typically limited to speeds under 55 mph. your manual will tell you it should ONLY be used on loose slippery surfaces such as snow/ice, gravel, sand etc. It should NOT be used on pavement unless one of those conditions exists.
At 28 ft, I suggest you look at a built in anti-sway device such as Equalizer. A friction bar is probably not sufficient.
2013 Coachmen Freedom Express 320BHDS pulled by a 2005 F250 King Ranch CC
A rainy day camping is better than a sunny day at work.