Thankyou for your comments I must admit Iam in the camp of thinking it could be just a way of getting you to part with your money, as said as above I have also towed for a long time, over fifty years, at one stage averaging 25k a year never had stone chip only had one blowout, so perhaps I,am lucky, its your van and you want to protect what is a very expensive investment, I dont blame you. In the 80s I tried something similar, I could open the three front windows (Buccaneer) and then wrap cling film round them, close them and lock them tight, when on pitch open and unwrap, result nice clean windows.