All,
a brief check of the manual reveals a „full load“ weight of 458kg/1009lbs and according the manual, the SS9+ has a dry weight of 275kg/606lbs => 183kg/403lbs of load.
SS9 standard 282kg/621lbs => 176kg/388lbs. Tables can be found on page 65 / technical specs.
So 183kg/176kg (SS9+/SS9) is the max load for rider & passenger with full gear including any baggage. Decide for yourself if you can make it with your passenger.
Just if you do it is advisable to adjust the suspension to have roughly 1/3 negative shock travel. Anything else will severely impact the riding and handling behaviors.
I would expect Energica to undergo some kind of max load test for bike homologation, so I guess those max loads can be considered as safe. It‘s also crystal clear that a lightweight rider with a heavy passenger will induce different frame forces compared with a heavy rider and a lightweight passenger, even though the total weight might be identical. Anyway, this should not affect the durability of the bike.
Don’t forget: It most certainly will have an effect on the riding behavior!