I have to think that this sort of thing must a freak occurrance and there should not be much to worry about with a matched tractor/loader pair. If you had the bucket chained to an immovable object and tried to lift it, and assuming you had enough rear ballast to keep the tractor on the ground, the hydraulics should just stall and fluid bypass through the relief valve. If the loader is strong enough to break a sound tractor in half, then it is too big for the tractor IMHO, and I doubt that such a situation would occur if one sticks with the manufacturer's recommended loader on their machine. I would say that brg's TC33D breaking in half was a very unfortunate case of a manufacturing defect that went un-noticed at the factory.
Having said that, one does still need to exercise caution when travelling with heavy loads as bouncing over bumps can exert more force on everything than the hydraulics alone can.
Brad.