No idea, I never drove it like that. When I initially complained to the Vauxhall dealer they contacted Vauxhall UK who suggested fitting springs/dampers from one of the German models - this did improve things solo but not towing - I've no idea what the difference was between UK and German models of the Astra but mine was a saloon version, exceedingly rare in the UK.Surely the back end of the car pitched up and down just as much when not towing but with the boot filled to the brim?