I attempted to ship small merchandise from USA to Australia today. Selected USPS-One Balance and Intl Large Envelope/Flat - Merchandise from the drop down lists. Entered weight of 1 lb 3 oz, but got error message "Invalid Rate. Mailpiece is over maximum weight of 4 lb 6.4 oz".  Note that 4 lb 6.4 oz is 2 kg, but the package is less than 2 kg. It's as if ShippingEasy is interpreting the 1 lb as 1 kg. Ended up having to send it via Package rate which was much more expensive.