Thanks, I've thought of those but my wife didn't like the idea! Perhaps if the box looks like it belongs on the trailer she'd go for it. It would make the trailer more useful for the occasional haul of other things. The Prius isn't rated for towing as far as I know, but I plan to keep weights (including trailer) under 1,000lbs. The rear cargo hitch box would help, but doesn't add enough space to be really useful. It would still be a tight fit.