Thom Stewart wrote:
If you use the solid vange to hold up the boom when using it for a
crane, it will soon be like Neals Boom, with a pipe in it. The topping
lift bears the load. The boom only position the lifting location.

Not if it was built properly in the first place.

I must be more spoiled than I realize, having sailed boats with strong
spars and decent rigging. Oh well.

If your boom will not lift a dinghy then it will not stand up to hard
sailing either. A topping lift might "bear the load" but it also puts
the boom under more compression than the weight of the load.

The usual failure point (in my experience) is the gooseneck.

Fresh Breezes- Doug King