With full size vans you have to watch out for the rear overhang and the position of the rear axle. Take a look at some and you will see that some have much more behind the axle than others. Of the top of my head, think the Ford 15pax versus the Chevy 12pax. The Chevy axle is near the rear doors. A long overhang places the hitch way back and places additional leverage, causing a more pronounced front end lifting effect due to the tongue weight. On a truck, the difference in the long vs short bed is accounted for in front of the rear axle. Just my $.02