I'm sure I saw a documentary years ago explaining the size difference between the 2 cockpits. I thought it might of been Spitfire! Two seconds to kill but having seen it again it doesn't look like it. I'm sure it's in my video collection somewhere!
http://www.bbc.co.uk/archive/battleo...in/11405.shtml
If memory serves, the Spitfire had a slightly larger cockpit but the 109 had a better engine layout and was easier for ground crew to work on.