MANKATO — Mankato posted an eight-run second inning and a five-run seventh to split a Northwoods League Great Plains West Division series with the Willmar Stingers on Monday. That pair of big innings helped the host MoonDogs earn a 14-6 victory at ISG Field. Mankato, which is 15-19, and the Stingers, who are 16-20, are both eight games behind St. Cloud. St. Cloud, which already won the division’s first half title, is the Great Plains West’s lead…