Hi all I'm building a new enclosure & I have fitted the plastic glass track to the enclosure, large track on top. I have a distance between the inside of the track (I.E. the opening area) of 481mm, what size glass doors do I need to order? Is there a guide that I should work too? I 'guesstimated' that I would need them 491mm high which would allow for the glass to sit inside the track comfortably?