comparative clauses

[Fredson]

I have the following sentences and I am not sure about how to analyze them:

Airlines obviously have to use their equipment as efficiently as possible.
--S--- ---A---- -----V------ ------DO------ ----------A-----------

or:

Airlines obviously have to use their equipment as efficiently as possible.
---S-- ----A--- -----V------ ------DO------ -------pred-C----------


or:

Airlines obviously have to use their equipment as efficiently as possible.
---S-- ----A---- ----V------ ------DO------ -------OC--------------


Could you please tell me, which of these examples is right.
Or another example:

Seriously, you should work much harder than last year.
----A---- -S- -----V----- ------pred-C or A--------



I think to see the comparative clause as an Adverbial would be right, because you can leave it away, right? But then it changes the sentence semantically.
To see it as an predicator complement would be right, because it describes the verb, right?
What about the possibility of it being an Objective Complement in the first sentence?