I put a chain through the rear subframe, in front of the rubber cone & link it together with a D shakle, the i attach a 2000KG ratchet strap the the castor bars & run it around a 1 inch square peice of tube on the front of my trailer, and ratchet it tight, it pulls the car forward & locks it solid.
3 trips to Melbourne, 1 to Brisbane, 8 to Hay & hundreds of trips round Sydney & the car has never moved a milimetre, i recently tried strapping over the wheels to allow the cars suspension to work to absorb the bump, big mistake as the trailer got light over bumps & wanted to sway at 110kph, i crap basically.
Saying all that it depends on how the trailer you are using is equiped with mounting points.
Here's a few pics of how i attach cars to trailer
Doogie
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I won Hay once, here's the pic to prove it..
Hay, it's not about the car, it's not about the venue, it's about the people that come here. Peter Dwyer, Mayor of Hay NSW.