PS4 for the 757F cargo : when you load via the ACE the unit weight for each lower deck container and main deck container and then load your 757F, then load in "real time" the 15 lower deck containers and 15 main deck containers (is fun one time only) then save to reinitialise your flight with the new load, and if you check your aircraft fuel & payload figures, you will see your payload is a lot short of the ACE figure, this is because the ACE is missing 2 main deck containers entries. I counted only 13 entries instead of 15 loaded, probably a bug. So this is why I use a plugin weight that I enter in FSX to come up the the correct max payload. (see the details in the 757F block)

Also when changing from flight assignements (full fuel flight and then max payload for instance) instead of having to unload "live" all containers, change the unit weight in ACE then reload them again, you can leave them all boarded, change the new value of each unit in ACE, load your aircraft, open the "live" loading menu/icon then without changing anything just press "save" to reinitialise your flight with the new payload you want. /which will be based on the number of containers boarded x unit weight as found in the ACE)