USPS International First Class BarCodes not Scannable by USPS

I have been using Shiprush for over a year and have been plagued by this issue since day 1. The USPS International First Class BarCodes are too small and cannot be scanned by the USPS employees. This requires they manually type the package number in order to scan the package. I am using a 4X6 thermal label. I tried using a laser printer but it continued to print in the same size. How can I rectify this? Do I need a larger printer for International First Class Labels?

The problem is even if I insure a package and it never gets scanned at the Miami International Sort Facility I cannot claim the insurance since there is no proof I mailed it.