The only thing that will eliminate it completely is to put your TT up on blocks with the suspension off the ground.
However, wheel chocks, properly used will significantly reduce rocking. 'X' chocks are very good, but simply placing a chock in front of the wheels, pulling up on it a bit, then placing a chock on the back of the wheel or back of the tandem wheel, then letting the TT settle in the middle works well too. Yes, you need to chock both sides for maximum effectiveness.
Additionally, placing another set of stabilizers near the axels will help a lot too.