Hi Radarman,
On my boat the tiller itself is 1240mm long, but the extension is attached about 95mm back from the end, however, the other end of the tiller (at the rudder stock) doesn’t quite reach the line projected above the pintle and gudgeon, so say 1200mm.
The tiller extension (on mine) is telescopic, and is about 720mm long when closed, and up to 1200mm when pulled out. I rarely/never sail with the extension fully closed, usually I would guess it’s about 75% extended.
I hope this helps.
DB