The selected and upvoted answer has not worked for me; after subtracting off canvas slot sizes for parent widgets I’m still consistently left with too large of a Maximum offset.
After further investigation with the help of someone on the Unreal Slackers Discord it appears that subtracting parent canvas slot sizes are not actually providing the size of the visible geometry for ScrollBoxes inside other container/parent widgets.
The solution for these cases is to make use of the CachedGeometry exposed to blueprints for the ScrollBox and getting the local size, as so:
