I am using Zen Cart 1.5.1 and have the new USPS shipping module installed. However, we are getting some very high shipping quotes on orders coming through our site. I understand USPS raised prices (at least internationally), but I'm talking about what the customer is paying vs what we actually pay. For instance, here is a breakdown of some pricing:

FIRST CLASS INTERNATIONAL
Japan: 9oz CUSTOMER PAID: $12.75 WE PAID: $6.30
UK: 7oz CUSTOMER PAID: $12.75 WE PAID: $7.15
Canada: 12oz CUSTOMER PAID: $9.15 WE PAID: $4.35

The way we get the shipping cost is by weight, which we generally give an average weight to all products (we sell shirts) and then add a small percentage to each attribute to account for the weight. For instance, the average shirt weighs .5 lbs, but if we're selling a 5X-Large, we add in .4 to the attribute so the final weight is .9 lbs, which should be how USPS calculates the prices.

That said, once we started noticing the skewed numbers on the site, I began testing some different weights and addresses to see where the problem is. The strangest thing is, if I set the base product weight to "0" in the product set up, I still get a shipping quote. If we are basing shipping on weight, and the weight is "0", what is the cost being based on? Not only that, but the prices that are coming up are still to high.

For example:

Canada: 12oz package shipping cost (First Class Int'l) $4.35 (BASED ON ORIGINAL WEIGHTED PRODUCT)
Canada: 0oz package shipping cost (First Class Int'l) $6.55
ACTUAL COST (package weighed 12oz): $4.35

So, at NO WEIGHT, the package still comes in at $2 more than it cost to actually ship.

Is there something wrong with the module, or is there another issue I'm not understanding?
Canada: 12oz CUSTOMER PAID: $9.15 WE PAID: $4.35