Two things that greately affect handling are Tire Pressure.. DO not look at the sidewall of the tire, DO NOT look at the sticker in the RV. Drive to a scale and get the axle weight, or better yet the wheel weights and then use the tire maker's inflation chart based on the actual load on the tire.
Another device you might consider is a track bar.. Leaf Spring Suspension has a tendency to, well "Wag" or Wiggle side to side a bit (The body can move sideways over the axle not just up and down) the Track bar kills this 100%