Has anyone any bright ideas as to how to keep the sun out of the caravan whilst it is laid up? Obviously we close the roof shades, but on the windows it says in the manual not to leave the blinds down as it will ruin the spring tension, and our curtains are for show only and do not pull across. This leaves net curtains in place, but we also wedge bits of corrugated card in place to keep the sun from fading the interior, but there must be a better way?