I wanted to come back around to this. The frame should never be used to secure a vehicle when transporting on a trailer. The problem is you cannot fully load the suspension. Hitting a pothole etc might compress the suspension further, allowing for slack in the tiedown and the possibility it may become disconnected.Tie the axles and wheels down NOT the body.
Any bumps and bounces will be transfered to the suspension which is made for that, the chassis hard points are not meant for long term restraint.