Agree my E450 is very solid and do not use any stabilizer jacks. Like Sam says different people may feel motion others miss. I have noticed setting parking brake eliminates some motion front to back. There is always a little roll in drivetrain if in Park so parking brake helps this.
Will Notice a little motion when we have had two teenagers sleeping in the bunk but again the parking brake dampens most of that.
Suggest you try it and see how sensitive you are. The motion is Nothing like a trailer shakes. Have only wanted leveling jacks when more than 3 boards are needed under tires to level unit.
