The law requires tire manufacturers to state the maximum weight that the tire can carry. So if you have two tires on an axle (left and right) then you add their load ratings.

Also check the maximum allowable payload for your vehicle.

Without the Starex manual on hand, I'd say its possible to transport the goods you are considering [it was designed to carry nine passengers plus their luggage]. Just try to center them over the rear axle for good weight distribution.

Stack the load as low as possible to keep your center of gravity low.