I haven't really seen an Eeco with a roof box but roof racks are definitely common. Now that I imagine an Eeco with a roof box the van looks a bit odd with it due to its basic style. And since you use it for delivering goods, installing a box which will have a lid will restrict the number of items you can put in the box even if they may be light in weight.
Different roof racks have different capacities. However, you also need to check the load-carrying capacity of your vehicle's roof which comes in the user's manual. Once you know both you will be able to do the calculations.
Different roof racks have different capacities. However, you also need to check the load-carrying capacity of your vehicle's roof which comes in the user's manual. Once you know both you will be able to do the calculations.