Ok, total fuel, flares, IAS, bearing, and 4 digits alt above sea level are showing in the 5 option boxes. I'd hoped to use the Comms boxes for chaff/flares but they get weird below 11 as they want to display 'Lo'.
There's plenty of examples of DED being exported out there so should be possible, aiming to have the entered-box display on the scratchpad, active steerpoint in a comms box and something else useful on the other. Would still like to do dynamic things with the scratchpad but first things first.
e: Now have working chaff, flares, steerpoint, fuel totaliser, velocity, alititude, bearing, distance to target, and time to target, however they're dependent on the active HUD and crash the UFC if you hit dogfight. Almost there...