I must admit mine does ride better with a couple of bags of cement in the boot.
Yes, going faster helps, but problems with speed limit.

Tried lower tyre pressure. If anything made it worse. So waiting till tyres need replacing.
(Present tyres continental as delivered)

My real annoyance stems from rear suspension noise (As if a spare tyre is bouncing around)
when driving over a series of small hollows in the road. (Similar to a worn out Camry)
Even driving very slowly over speed bumps creates a "Plop noise" once rear wheels come back down on
the road surface.