Robfrey,
I guess if you tie to the chassis , compressing the suspension it is possible and even likely that things may loosen up because of suspension travel etc..
On the Vicky, I use axle straps over the rear end, pulling it down and to the rear of the trailer, in the front I use axle straps over the front (straight axle) pulling down and forward. This way the chassis is not moving in any direction,,, yes the body of the car may "bounce" on it's own suspension, and the trailer may bounce on it's own suspension, but the chassis of the car ain't moving (I sure hope not) some will say the down side to this method is putting all the down force on the tires !!!
For Maxton, it's only a 2.5 hour haul for me,,, so for Maine and Bonneville,, I will use shop tires while trailering,, changing to the race tires upon arrival at the track.
Charles