Fannie Mae last month settled the largest-ever non-agency MBS, an $11.703 billion re-securitization of 19 subprime mortgage deals in its investment portfolio, although most of the transaction will stay on the government-sponsored enterprise’s books. Fannie Mae Grantor Trust 2004-5 is backed by senior AAA-rated subprime MBS classes the GSE acquired over the past few years from such lender issuers as Ameriquest, Option One, Countrywide and Long