We've added the shipping weight of the package to the shipping screen, so if you need to increase the weight because you have a heavier than normal game, you can do it from that screen.
If you are changing the weight, make sure you weigh the entire package, including any packaging or tape you've added.
We don't currently allow you to decrease the weight below the default weight we have for that game. This is just a precaution to avoid problems with the post office returning packages that are weighed incorrectly. If you know the weight is lower than what we have listed, you can send us a message or email us at firstname.lastname@example.org and we can manually changes the weight for that game.
Packages up to 7oz are included in the base shipping price, but once you go to 8oz and higher there is an increase shipping cost to pay for the higher shipping charges from the post office. Once you go over 13oz then the cost also increases since we have to move from the cheaper first class mail to the more expensive priority mail shipping. (That should only happen when shipping multiple games)
Every time a user changes the weight for a trade, we get updated and we can choose to save that new weight permanently so all future trades for that game will use the updated weight.