I would just use a trailer with a mast support at each end. I have hauled just a mast with my cat trailer that way and the front of the mast can go over the car. I would not like to depend on lashing to hold the trailers together and if the mast starts to wobble in the middle the rear trailer will start the sway. If you drive all the way to get the mast and your system does not work you won't be happy. Use something that has been done before.