The only way to tie down a vehicle unsuspended, would be to tie off to the control arms in the front. Or those wheel straps. Which in an enclosed trailer there would be nowhere to tie them down. And if there was, your still hooked to the control arms. There is no way I would ever do that to our chrome moly control arms. Your putting a lot of tension on there with ratchet straps. Drove a truck hauling cars for many years. All the multi car hauling trailers I used Had J hooks, on chains, on a ratcheting wench set up. The clearance underneath is very minimal. If you didn't pull down the suspension. The cars would beat themselves to death under there. In our enclosed trailer. The tie downs are so far out in front and back, on a car anyway. That in no way, are you going to be pulling straight down anyway. By angling the straps, and having them long. The car moves very little, in a controlled manner. While, from it being in a long angle. It lets the car move up and down minimally, and does not allow the straps to come loose, or beat up on your suspension.