[skyking]

1: Do not shorten the tongue. Too much work, structural, low payoff.
2: build a splitter for it instead. use metal or lumber, build a triangle at same height as front of curved front, and use two panels as sides. Now the crosswinds will not cause as much trouble there.
3: build simple three panel boat tail for trooper, that goes back 4' and is above that splitter with a safe clearance for odd driveways, etc. let's say 6"
Angle it at 12 degrees down and in on sides. More than that and it will separate.
This will manage the flow off the trooper, reduce the trooper's wake, and deliver it onto #4
4: roof over trailer as you planned. curve it down slowly all the way back, and make it open up where you need. Even if you have to grab the screw gun to open it up, finish it off as smooth as you can.

Anything else beyond that will be of limited return. I would not bother covering the trailer wheels, when you look at the running board construction and other things that are already crapping up the air there.

See splitter detail below. three pieces of metal/wood, two panels. Leave top open unless you have panel material to spare.
Now it will work more like this motorcycle trailer in the second pic.