Is Prolegomena Permissible?

I was reading Covenant's own Dr. Michael Williams on the matter of systematic theology, and he covers a lot of very good ground. However he raises a question that I have struggled with for some time: should systematic theology burden Scripture with extra-scriptural prolegomena? That is not far from the problem Barth dealt with as he sought to have the Bible provide not just the answers, but also the questions for theology.

I would suggest that we must have prolegomena. We cannot come to the text tabla rosa, we will apply an interpretive framework to it. We bring our cultural and linguistic frameworks to the text; we bring our epistemological frameworks to the text; yes, we even bring our understanding of the text to the text. The hermeneutical spiral is what it is regardless of if we wished we could simply extract the text as we was meant to be known. I know Dr. Williams acknowledges this as well, and, for that matter, we have spent much of this semester in what appears to me to be the prolegomena of Covenant Theology, and so I am sure there is more to his position than what I have stated above. I need to talk to him on this subject perhaps, but I leave it to my readers for tonight: how do you deal with the tension between sola scriptura and the need for interpretive frameworks in reading that Scripture?

For me, I think, following Calvin and the Westminster Confession, I find it mostly helpful not to look solely to Scripture, but rather to place whatever I look at under the authority of Scripture. I would argue we must have extrabiblical assumptions, but that does not mean we abandon sola scriptura. What do you think?