Black widow is a 500 lbs rated carrier but is much stronger with teh outriggers.
https://www.discountramps.com/black-...hoCrioQAvD_BwE
This is a high-quality box. The paint could be better but you don't want much heavier than this.
https://www.harborfreight.com/2-34-c...hoCp00QAvD_BwE
I lengthened the width (to get near the full width of the van) and narrowed the depth to fit between the carried and the van. I also added a 5 gal jerry can carrier.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
https://www.harborfreight.com/500-lb...ier-66983.html
Ramps store as original behind the motorcycle but in front of the box.
The DRZ400 weighs about 300lbs so I can still get it up the ramp between the close quarters to the box. The box paid off the first time I unloaded teh DRZ because of a strap malfunction the bike was released completely on one side but the box kept the bike from falling off.
If it was a 500 lbs adventure bike with bags it might not fit (bags would need removing) depends on the bike.
I also put trailer lights on the carrier and will move the license to the box when it is installed (marker lights and bulb for the license).