hi we are annie & martin our set up is a vectra 2.0 petrol with a coachman 520/4 we have just come back from our first time out in our van we traveled 165 miles to skeggness & back.annie towed the van all the way there & back with now problems except when a lorry passed us at speed on the way back and made the van snake bad for a second we all most lost it. could anyone tell us the best way to stop a van from snaking when it starts please.