There are several things you can do to get a better ride.
I run 21-22 psi in the rear tires, all the time. Even 2-up and loaded for a 6 week trip. Gravel road, asphalt, tearing thru curves. At first I thought lowering the PSI that low would pop a bead in hard cornering. We've ridden well over 100K miles with no issues.
Well, I say no issues, BUT the center of the tread will wear out faster at those lower PSI's. But that means 50k out of a pair of tires instead of 60k.
There are also other tires, the Goodyear Comfortred, that have a softer sidewall and provide a smoother ride. In those I run 23-24, otherwise they wallow too much in the curves.
Front tires I run the recommended...36 on the OEM and 40 on the Avon.
In addition you can soften up the bumps some with a Convertible Comfort Lift™ which you can see
HERE.
The best thing you can do is get some Trike Series Shocks™. Shocks that were specifically designed for the Harley Trikes to give the most comfortable ride And a more stable/flatter ride. You can see details on them
HERE.
There is a full report on Rear Suspension that you may find useful
HERE.
Here's just one of the vids we have on Trike Rear Suspension...this shows some testing-
Kevin