[skyking]

I have some ideas for a telescoping fairing system that clips to the trailer on each side, and uses bungees for most of the sliding features. The big trick is allowing for the trailer to roll on a different plane than the car, as when crossing in and out of driveways at the very infrequent fuel stops
As others have suggested, I'd go with a mild (easy to build) convex nose that will serve you OK on any tow vehicle. The fairing system would adapt to that if and when you can.
As to the open box termination:
I plan on that with my trailer build for a couple of nice features.
1) crisp separation
2) relatively easy to add a folding tail to. The fittings go under the edge and are clean and out of sight. I plan on a 4 panel tail with open bottom so the bikes can still hang on the back OK.