It's a fact that, by virtue of design type, a semi-float axle carrying the same load as a full-float axle is under significantly more stress than the full-float axle.
The axle shafts and axle bearings of a full-float axle are only holding up the axle shaft itself and transferring torque from the ring gear carrier to the wheel hub. They are not holding up the weight of the vehicle and it's load.
A semi-float axle shaft and it's bearings are not only transmitting torque, but also holding up the weight of the vehicle and it's load. They're doing double duty.
In a full-float axle, the axle housing/spindle, hub and hub bearings are holding up the weight of the vehicle and it's load.
If a semi-float axle were such a great design for heavy load carrying, there would not be full-float axles used in all commercial trucks from class 4 through 8/9, as well as almost all class 3 (your E350 van is one notable exception) and overwhelmingly most class 2. The heavy load carrying classes are exclusively the domain of the full-float axle design.