[aerohead]

yes,the long length has always been the bugaboo of truly low-drag vehicles.It's why Kamm and Fachsenfeld spent so much time researching cost/benefit for varying lengths.
Kamm/Fachsenfeld settled for a car body which followed a streamlined pathway,then was chopped off at a point where the new wake area was 50% of the car's frontal area.
The Fachsenfeld went one better,creating an inflatable boat tail which would only deploy on the highway,far from parking garages,traffic,etc..
With the stinger,my truck will be 311.6-inches in length.
With only the boat-tail,269.6".
The longest vehicle on the road today is a 2012 Dodge RAM Laramie Longhorn DRW pickup,at 259.4".
At 30-mph a tail won't do you much good.I don't know what to recommend.