The special treatment for overlay aerial is quite different. Packaging is problematic when a module reads a file, but that process results in reading additional files (as with shapefiles). This also occurs with imagery when orthorectified images include an image file and a georeferencing file (e.g. world file, .gcp file, etc.).
To resolve this, overlay aerial’s “Convert to Packaged” button creates a GeoTIFF file that is both cropped and matched to the specified resolution in overlay aerial. This creates a new single image file which is generally dramatically smaller than the original files which were read. Your application is unchanged except that the Filename specified in overlay aerial will reference the new packaged geotiff file created by this process.