The National Association of Federal Credit Unions Monday sent a letter to the Federal Reserve Board supporting a proposed rule that would increase the escrow threshold for jumbo loans. The organization said the rule would help credit unions “better manage interest rate risk relative to higher-priced mortgages.” Under the proposal, loans that exceed the Freddie Mac maximum prinicpal limit — $729,750 — the escrow requirements would apply only if the annual percentage rate is 2.5% or higher than the applicable average prime offer rate. The proposed rule comes from Section 1461 of the Dodd-Frank Act. Write to Christine Ricciardi.