I am having an issue using the FUEL CROSS FEED SimVar in the SimVar Watcher. It shows it as an Enum, not settable but responding to read access. I took this to mean that I can see changes in the SimVar Watcher for that SimConnect variable if I change it on and off on the HUD of a 787 Dreamliner. Unfortunately, the button does not show any change. Does this SimVar work? Does it currently only work in certain aircraft?