When I was pulling hoppers there was a guy who had them on his set, you can't run as heavy with super singles as you can duals because the tire isn't rated for the weight, on a single axle set like on a pup, if you blow a tire you'll lose control. Even on a tandem axle group if you blow a tire you're done and not moving until a service truck shows up, along with that, nine times out of ten you'll ruin the wheel and fukk up your trailer in a bad way when a 500 pound tire tears the schit out of it. Duals give you better traction on snow and ice, you can actually carry what an axle is rated for with duals, if you blow a dual you can limp to a tire shop, and they're a lot cheaper than a SS. maybe on a reefer @ 80,000 pounds weight isn't such a big deal, but with farm commodities or anything else hoppers normally haul, being able to haul what your set can bridge is a major thing. I still maintain that they're a schitty idea.