The USPS K8 January 17, 2016 module has a few quirks related to the First Class for > 13 oz and < 16 oz ...

If you look at post #17 on:
https://www.zen-cart.com/showthread....z-lt-15-999-oz

I have a solution to test ...

Please keep discussion for the First Class for > 13 oz and < 16 oz issue on that other thread, for now ...