So I had some more crazy ideas...
Fer the front amber light, I can cut a rectangular hole in the Coroplast and mount the light from the back. The amber side marker should still be very visible and it should reduce the amount of possible air disturbance from the marker light housing if it was surface mounted.
To reduce the length of gap cover from the truck to the trailer, I'm gonna install some hinged doors attached to the trailer that should reduce the amount of gap cover attached to the truck. I might be able to git away with a 12"-16" door. When I need access to the trailer hitch, the door swings open to reveal access. I'll probably have to use either bungee cord or some sort of pin lock to keep the doors secured. Gonna give this idea a shot in the morning.