I regularly exceed my maximum load on my van, what must I do to increase it's maximum permitted load?

I have some heavy machinary installed but recently I seem to carry too many extras. The permitted max weight is 2800 kilos yesterday I weighed it loaded and it was over 3000 without driver and penger, it is a short wheel base Peugeot boxer, I believe Peugeot do make Boxers with a max weight of 3500 kilos. I have reinforced the suspension.