Trucking industry has known for decades that as long as 1 tire has the capacity to carry the load, 1 will use less fuel than 2. But for many other factors cause them to stay with duals.
IMHO, if a blowout on trailer causes you to loose control or roll your rig you didn't have control before the blowout. (Fact is the rear axle of TV is where a blowout is most likely to cause loss of control) Just trumping here, but I think there is a better chance with single axle that the driver would notice a issue with all the tires on one side, pull over and stop before the tire beats the snot out of trailer.
Single axle takes less power to turn, because don't need to force axles out of line or slip tires sideways. If fenders are inside body, tandem will use more space.
I buy 1 trailer tire a year, get rid of when 3 YO. But I know a guy that will give me over 50% for my take-offs. His hands feed enough tires to curbs he gets almost new life out of them.
