Here is the CAD file for a front window with a port hole for the vent: http://www.acwmotorsportplastics.co.uk/polycarbonate-pop-out-vent.html (http://www.acwmotorsportplastics.co.uk/polycarbonate-pop-out-vent.html)
I've finally got round to doing the standard opening front window drawing. There are 'top' and 'bottom' window drawings attached.