Any chance you could send me the code so I can play with setting up some custom displays? I'm also happy to make a request, as it seems you made custom screens for others.
One of the first things I noticed was the the configuration menu remains in metric when the unit is set to imperial. My experience with the base mpguino is that it simply inverts the calculations, and does not make a unit volume adjustment. If doing a partial fill of, say, 5 gallons, do I put in 5000 "liters", or 18925? Or 22710? If the device is doing the conversions itself between gallons and liters, you'll need a way to specify whether it's a US or UK gallon, because they're different volumes.
I imagine that, since very few people will likely be switching back and forth between metric and imperial, it may be fine to simply rename the volume unit in the fill-up section, rather than do a unit conversion. There won't be any dealing with different gallons.
Another thing - Aerocivic gets much better fuel economy than most cars, and the graph is constantly off the chart while driving. It would be nice if this were somehow adjustable by the user, either as a setting in the menu or in the setup screen. Realistically, Aerocivic would need to display values as high as 120-150mpg (2.0 - 1.5L/100km) for even slight downgrades.