I have performed this guide extension on my Scaley Megane, and a few other cars... It seems very robust, though I have just a few laps on it.
From Chris Brigg's page http://jbriggsk9.tripod.com/chrisbriggsslotcarpage/id7.html
From Chris Brigg's page http://jbriggsk9.tripod.com/chrisbriggsslotcarpage/id7.html
