The nv200 has a payload of 740-750kg depending on which version.
With respect to bravo20, i would strongly suspect a full 500l tank would take the van well over the gvw. So unless he has been on a weighbridge and knows this not to be the case, i would recommend no more than a 350l tank.
My transit connect has a 900kg payload and with a full 500l tank i am 40kg under my gvw according to a customers weighbridge.
You have been warned!