Mk I Spitfire canopy length

Hi all

A colleague of mine is reconstructing the lower part of the canopy from a Mk I Spitfire that crashed in Peterborough http://www.bbc.co.uk/news/uk-england-cambridgeshire-37440619

There are several fragments of the lower sliding portion which appear to fit together although the length seems excessive. Can anyone enlighten me as to the correct length of the lower canopy frame?

TIA

John