International shipping weight is always off

99.9% of the time domestic customers pay $2 extra for shipping. This makes up for the cost of boxes, kraft paper, bubble wrap, or anything else I need to package the order. International customers, on the other hand, are always right on the line. Many times, I actually lose money on shipping. Today, I lost $10, which is not much in the grand scheme of things, but $10 adds up fairly quickly.

Is there a way I can tack on an extra buck or two to just international orders? Any help would be appreciated. Thank you!

Someone maybe able to advise a free way but this http://ceon.net/software/business/zen-cart/advanced-shipper will pat for itself in no time by the looks of it in your situation.

USPS RateV4 and IntlRateV2 Shipping Module

This module has separate additional fee fields for domestic and international. Also allows other USPS options to be added.

We've been using it for over a year and are very happy since it allows us to filter/sort by product volume so that smaller flatrate boxes are removed as options when their volume is exceeded.

ONE CAVEAT, USPS Jan 2012 changed the word parcel/package in their tables and the module must be edited to make that change or International First Class packages/parcels will not work.