(Editor's Note: This story has been updated to reflect the correct name and rank of the Army's program manager for Stryker future capabilities.) The Army's top acquisition official has approved the purchase of a fourth brigade of Stryker vehicles with the double-V hull, the Army announced on Monday. Acquisition chief Heidi Shyu approved the plan, which involves swapping out upwards of 360 vehicles as part of the Stryker Exchange Program, according to the announcement. The exchange program takes flat-bottom...