i have a 2018 Bounder 36D, it will rattle your teeth on a ruff road, would sumo springs help? Also it can be difficult staying in your lane in wind or when passed by a 18 wheeler. Does the steering stablizer work, what about adding up graded stabilizer bars any 9ne had good luck with these? I’m bleeding money right now getting the toad set up and all ththe other cost, I want a better ride with out breaking the bank and sure could use some advice this is our first motor home. 

I have a 2018 Southwind 36P which should be very similar to yours, it has a 252 inch wheelbase on a 30k chassis.

I previously had a 34' on a 26k chassis. I have never experienced what you are talking about. There is no sway at all when a truck passes and the Rv handles well on twisty roads with little sway, the ride is o.k. unless there are really bad bumps.I can normally drive with one hand with no problems at all. 

Before spending a lot of money you might want to check your tire inflation and sway bar adjustment. It is best to be sure they are at recommended pressure and not the max printed on the tire. I run mine at 90 psi cold, they will go up as high as 110 hot. I also did the cheap handling fix on both of my units, it is easy and free and tightens up the sway bars some. There are several threads in most rv forums on the CHF  and utube videos. It is easy to do and takes about an hour or so.

I have also seen recommendations to have the alignment checked on new units, mine was o.k.

Good luck