Aspen Insurance Holdings Limited's three preferred stocks - AHL.PR.D, AHL.PR.E, and AHL.PR.F - are now backed by Sompo Holdings, a global insurer with A+ ratings. I am upgrading all three Aspen preferreds to Buy, citing ~7.4% yields and Sompo's robust financial backing and coverage ratios. Sompo's $101B in assets and 98x preferred dividend coverage ratio virtually eliminate non-payment risk for Aspen preferred shareholders.