Richard Hays' book: 'Echoes of Scripture in the Letters of Paul' is a fascinating read and in lots of instances I find his readings of Paul highly persuasive. Basically, he takes a literary approach to the text, looking for allusions (though he prefers the term echo, since it doesn't require authorial intent) to the OT. He doesn't want to restrict Paul to any one hermeneutical methods, claiming that he is driven much more by his hermeneutical goal, which Hays thinks is primarily ecclesiological.

Having recently read Walter Kaiser's 'The Use of the Old Testament in the New', I find myself very much in sympathy with this statement:

to read Scripture as a book of messianic testimonies that point to the crucified Messiah, Jesus, requires a great deal more ingenuity than to read it as a narration that foreshadows God's purpose to raise up a worldwide community of people who confess his sovereignty and manifest his justice.

You'll see that Hays thinks the narrative of the bible is all important, and in this he sees the gospel as the expression of God's righteousness which both incorporates the Gentiles and maintains his promises to the Jews.

Hays does allow for Pauline 'echoes' from non-scriptural texts such as Sirach and Wisdom of Solomon, but he pays little attention to these.

The really interesting point is whether and how far Paul's 'methodology' should be a model for our own interpretation of both Old and New Testaments. He breaks this question into three components:

(i) Are Paul's actual interpretations of scripture normative?
(ii) Are Paul's methods exemplary?
(iii) What are the appropriate constraints on interpretive freedom?

Some would say: No, No, GHE
This is certainly consistent but hardly satisfactory for Christians.

Others (Longenecker): Yes, No, GHE
This is profoundly unsatisfactory in my view - essentially Longenecker argues that Paul gets the right answers by the wrong methods! And since these methods are a fundamental part of his message (ecclesiological and eschatological hermeneutics) Longenecker ends by undermining Paul absolutely.

No one really thinks: No, Yes, ?
Although I wonder if some who try to argue for a 'trajectory' model for understanding women's ministry/homosexuality/etc. are close to this.

Hays thinks: Yes, Yes, theological constraints NOT methodological ones
I basically agree, though I think there are methodological constraints (actually so does Hays, kind of) to do with being a 'good reader' which involves a lot more than traditional GHE and recognises the importance of the community of faith as the intended audience with the necessary spiritual insight to interpret the word.