So, I think I may have figured out why things seem a bit whacked in GW3 and GW4 for the payload limitation calculator - it appears that it's taking into account winds when displaying the values rather than the "old school" way of no wind accounting being added. I'm seeing routes like EDDF-USNN-Somewhere in China in GW4 where the load limitation should be the same, but it's displaying as different from the open route editor.