At first, mine was around 190kg (11% of GVM).
I thought that was a bit on the fat side, so I rejigged my load distribution and got it down to 150kg at the hitch (8% of GVM).
next trip out it wagged its tail more than a happy Labrador, and I damned near rolled the thing.
It quickly got put back to 190kg, and tows like a dream.
It's not all about ball weight, weight distribution and handling dynamics also come into play. If that's how the manufacturer has designed it, and it tows well with that ball weight, perhaps the effort needs to into making sure the car can take the load rather than changing the trailer ?