Actually....
Though I am grasping at straws here is one of the drawings - I think it's mis-leading but rather than lead you lot; can anyone see what I mean before I post what I believe the drawing should be.....?????
@Onoff why an earth do I want to make the hole larger???!!!
@Triassic the thick black frame is meant to sit around the openning i.e. it's the actual part that goes on the up stands.