This image survived in my photo albums and will give a 'face' to the concept of a range-extending trailer.
Low drag and 'length' go together. Trailers add length. Streamline them and you get past the 'practical' length issue.
Any penalty from added rolling resistance is overwhelmed by the drag reduction, netting an overall range improvement.
https://ecomodder.com/forum/member-a...ed-micro-r.jpg