The nonprime mortgage-backed security issued by Deephaven Mortgage earlier this month was largely similar to a deal the firm issued in April, save for a greater emphasis on mortgages underwritten with less than full documentation. So-called alternative documentation mortgages accounted for 36.5 percent of the $250.13 million MBS Deephaven issued this month, up from a 17.7 percent share of its $221.14 million issuance in April. Non-agency lenders underwriting mortgages ...