3d cart doubling my USPS ounce weights

[Elipey]

I ship cosmetics and most are in ounces. I have set the decimal correction for ounces as 3d cart only ships in pounds. If an customer buys one lipstick, 3 oz the USPS shipping price is correct (around $2.71) but if they order 2 for 6 oz, the USPS transfers it over to priority mail automatically and charges them $10.20. Has anyone else experienced this problem, and if so, have you found a workaround. The shop I am coming from you could edit the USPS module but I have not found that module on the back end here.:eek:

[mondo]

I was interested so checked one of our light items.
the weight is .1875 in admin (also a 3 oz. item)
Added one to cart checked shipping first class OK.
Added second one to cart rechecked shipping and it offered first class properly for the 6 oz. weight.