I assume you would have (or would have) two wheels and two springs with the trailer.
An alternative would be to space the two springs closely together, and put the two wheels on a bogey.
http://ecomodder.com/forum/showthrea...hin-13142.html
Your plan reminds me of Dave Cloud's Dolphin. It had closely spaced wheels, although not as close as you propose.
Notice the skegs. The overall shape concludes in a flat tail, but there are vertical elements acting as wheel spats.