Trailers are designed with tandem axles because one axle can't carry the load of the trailer, not to provide greater stability. When turning while pulling a tandem the axles are not aligned with the center of rotation - they can't be because the axles are parallel. The tires want to go in a different direction than the rotation of the turn and must, to some degree, scrub to make the turn. This is why maneuvering them by hand is so difficult. The same thing is happening when being towed but the power of the tow vehicle forces the tires in the direction of the turn. This scrubbing action deteriorates stability, not enhances it.

Tom

Trailers are designed with tandem axles because one axle can't carry the load of the trailer, not to provide greater stability.
I call 'hog-wash' on this one! There are a few trailers by the same manufacturer with the same glider inside in the exactly the same configuration but they have a single axle with larger wheels. The load bearing capability is the the same in both cases. Going to a tandem axle enhances stability (tracking) and allows the whole trailer to sit lower since the wheels on the tandem axle are typically smaller. Lower CoG = more stability.
I completely agree with your point of them being a pain in the butt to man-handle them.

Uli
'AS'