Redwood Trust worked for years to revive the jumbo MBS market by issuing deals with super-prime mortgages. Now, the firm is shifting its focus somewhat to “expanded prime” mortgages that have slightly looser underwriting standards. The $316.49 million Sequoia Mortgage Trust 2017-CH-1 is the first MBS from Redwood to deviate from super-prime standards. The deal received preliminary AAA ratings this week from Kroll Bond Rating Agency and Moody’s Investors Service. The average combined loan-to-value ratio of the mortgages in the MBS is...