The jumbo mortgage-backed security market is set for a significant boost as Flagstar Bank will issue MBS. Since 2015, only one bank has issued jumbo MBS: JPMorgan Chase. Other issuers have all been nonbanks as banks have largely opted to retain jumbos in portfolio instead of issue non-agency MBS.Some details about the planned Flagstar Mortgage Trust 2017-1 were revealed this week in documents filed with the Securities and Exchange Commission ...