Herbert finished two shots behind Mendez after falling five behind with six holes to play but an eagle and a birdie made up some of that gap.
Herbert's fellow Victorian Ryan Ruffells finished six shots from the lead in a share of 7th position.
In the 15-17 year olds for the girls West Australian Hannah Green was the only Australian to make the cut and she finished 10th.
The Sunshine Coast's Jack Trent led the Australians in the boys 13-14 year olds when he finished tied for 3rd.
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