If the mast is wood, you could wind a helix around it. If it has guy wires, you could insulate at the top and bottom and make a sloping V with multiple feeds to change direction.
Sure.... assume an infinite trailer roof. :)
Gunner may want to look at a grounded horizontal loop running around the perimeter of the trailer roof, far enough from the edge that the antenna isn't visible from the ground. Bring the end down the side of the trailer a couple of inches and put the tuning capacitor inside.
Look at the HF antenna on the Chinook as an example.
Third picture down:
You don't want to get too wrapped around the antenna. Down at those frequencies it takes a real big directional antenna- like a Beverage or a Rhombic- to make a big difference. (The one at work that was used to talk around the world is about the size of perhaps six football fields) Otherwise you are sucking in as much noise as signal.
Make sure you use Monster cable for good reception.
Kevin Gallimore