This may get interesting. Do you have a 10-year RV permit for the pickup and the trailer. That will really grease the skids officially. If you have the 180-day permit and go to turn in the TIP at the border and they see no trailer connected they are going to say, No Trailer No Cancellation.
Been there done that with the roof cover. Used corrugated green fiberglass patio roofing. 1/4" rivets with backing washers. Without a tree and a chain hoist your bill board is going to be a tough row to hoe. I used multiple Harbor Freight gray tarps, but left enough opening for ventilation. Creating a bat cave will grow mold that the Center For Disease Control would flee from.