Size of cleats or staples for 5/16 hardwood

Q: I got this 2-In-1 Flooring Nailer/Stapler (link here: http://www.harborfreight.com/2-in-1-flooring-air-nailer-stapler-97586.html) It worked fine with 3/4 thick Bellawood Brazilian cherry hardwood.

Now I am using 5/16 thick Bellawood Brazilian cherry and the tongues are getting damaged. I was using 2 inch staples. What is the size of cleats or staples recommended for 5/16 hardwood? Thanks.

A: I would go with 1 1/2 inch cleat.