In 1983 we bought a Toyota chassis motor home with single rear wheels (SRW). Through a half-breed recall, I later upgraded the rear axle to true duel rear wheels (DRW) with "D" rated tires. I've been very shy endorsing any motor home with SRW since. The VW chassis Rialta & Vista had SRW which had me shying away from them when shopping in 2005-2007. I just can't see a single rear wheel back there holding up a house, people, gear & food, fresh water, and tow something. Also adding a significant rear over-hang too. It just doesn't seem right.
Give it a year or two and I bet Dynamax will have replaced the SRW Dodge Promaster with the DRW Ford Transit. It only makes sense to do so.....unless Dodge introduces a HD DRW chassis.