While non-agency mortgage-backed security investors did not file a formal challenge to the $25.0 billion servicing settlement, they remain concerned with the implementation of principal forgiveness loan modifications. The latest qualms were raised last week in a letter to Shaun Donovan, secretary of the Department of Housing and Urban Development, from Sens. Sherrod Brown, D-OH, and Bob Corker, R-TN. “Because any settlement could dramatically affect [pension funds and retirement funds], their managers should ...