[aerohead]

Abner,I've looked over everything I have including buses and tractor-trailers and it's my opinion,that for your vehicle's Length-to-Height ratio,and it's general layout,that Cd 0.235 would be a reasonable minimum.
With a complete tail she might get to Cd 0.175.
Your form is essentially a 'Gavre' artillery projectile with added truncated boat-tail.
The nose and body,in free air would be Cd0.20
In ground proximity this would rise to Cd 0.40.
Adding 'skinny' wheels and tires would push it to Cd 0.44.
I allowed a 16.5% drag reduction for the catamaran wheel fairings and with your truncated boat-tail ending at 51% of frontal area she slips to Cd 0.235.
I would recommend you cut your lead wheel fairings back to something like 1.3 X tire width.Extending forward as they do,they can act like rudders in a wind gust,and under compromised weather conditions could introduce stability issues.
Frank Lockhart was killed in the Stutz Black Hawk which had such fairings and they are blamed for the crash.