When can verbal passives be used in secondary predicates?

In a paper I read, on the fifth page (labelled "359"), it says resultative secondary predicates can only be stative adjectival passives. For example, "John hammered the metal flat" is valid but "John hammered the metal flattened" is not. However, there are other secondary predicates that don't follow this rule. "I prefer my food salted" uses "salted," a resultative, as a secondary predicate. Also, "This software comes pre-installed by the manufacturer" is a valid sentence, but I don't think "pre-installed" is an adjectival passive, so I am not quite sure about the rules on secondary predicates and passives.

You're confusing terminology.

"John hammered the metal flat" is indeed a resultative construction: the hammering brings about the flatness.

But "I prefer/eat my food salted/hot" is an object-orientated depictive construction. My preferring/eating does not bring about the saltedness/hotness (though some prior process has done). And "This software comes pre-installed by the manufacturer" is a subject-orientated depictive construction, like "John arrived here totally exhausted."