The books are too heavy to be carried <= this sounds fine to me. No native speaker likes it?
You're right; my comment, though, was on the semantic structure of the passive structure:
1. The books are too heavy (for us) to carry. (Active) :D
2. The books are too heavy to be carried for us. (Passive) :(
=> 'by us' would have been the correct form. :wink:
3. The books are too heavy to be carried by us. :D
Of course, 2 is grammatical given a situation wherein someone asks to carry our books: "The books are too heavy to be carried for us (i.e. You shouldn't carry them for us; they're too heavy).
In short, 1. refers to "us" as the carriers (the ones doing the action), not the carriees (the ones having the action done for them).