Rough ride

A lot of threads on ride comfort. Do a search. Starts with knowing your weight and adjusting tire air pressure and just keeps on going.

Why not an air ride system?

Why not start with the free/inexpensive stuff:

What are your axle or wheel position (better) weights?

What tires do you have and what PSI is in them.

If well the tires are over-inflated, there is no silver bullet that will cure it.

Describe what a tank feels like :) Is it just bumpy? Vibrations? or?

Look, at the label, besides the Driver's position, or the door jam and adjust tire pressure to that, not maximum pressure, on sidewall.
If that doesn't do it, maybe you have too stiff, a tire, sidewall. Some run semi tires, stiff enough, for 50 tons. An RV spec tire will generally have more flexible sidewalls.
Look at shocks, are they gas? Gas units are stiffer.
Is the coach loaded yet? The weight affects it.

You've been a member since 2004. What did you have before that rode so much better?

Is it empty, or do you have it loaded for traveling? Sometimes even filling up the fresh water tank will help hold down the back end.

No question that on these shorter and lighter motorhomes a load helps the ride. Koni shocks can make a difference as they are not as stiff as Bilsteins and if you want to unload 6 grand the Kelderman air ride will make an enormous difference. These lighter shorter wheelbase motorhomes do not ride like the larger ones that have more weight so a lot of tweaking can get expensive to get them where you are comfortable. As had been indicated tire air pressure is critical. When the service rep put 95 into my tires instead of 80 even my Kelderman couldn't help it.

First, correct tire pressure for actual load.

Second, put on Koni FSD shocks.

OPPs

No offense to anyone, but I've been RVing since 1976 and never had a completely smooth riding RV. You have to keep in mind that driving a Class A or Class C you have a house mounted on a truck or bus frame and being a high profile vehicle your subject to wind and any bump on the road that you encounter is going to cause a rocking motion or a porpoising motion. There are expensive equipment that you can buy to limit these motions. And sometimes people forget that most roads are supered (angled for drainage) from the centerline to the shoulder. So your driving down the road at a slight angle. Good Luck in your attempt to get a smooth ride.