Reading through this thread I get the feeling that the distance of an audax depends on which version of autoroute has been used.
How can I find an under distance event that autoroute has approved???
My DIY 200 up to Cambridge and back is teetering on the edge, just using "Putney" and "Cambridge" wasn't good enough. I had to nominate specific controls at the South end of Putney and in the North-East of Cambridge to get it up to distance according to Autoroute.
Autoroute doesn't help itself by picking odd locations for towns. If you add "Broxbourne" as a control town it looks ok, but if you zoom in you see that you make a 400m detour down some sideroads to the exact spot Autoroute classes as "Broxbourne" then 400m back again to the road I was on to continue the journey, you only see this if you zoom in enough.
I also shave off a bit off the journey by using a cyclepath across some fields from Shelford into the back of Addenbrookes hospital that isn't routable on Autoroute. Even with this I've never done the one-way journey is less than 106km though because of my choice of route (avoiding the A10).
Going from Haslingfield to Cambridge, for example, will take you either via Barton or Harston. The quickest route, with local knowledge, is up Cantelupe Road, through Pemberton's Farm, over the M11 and into the back of Grantchester. That saves at least a mile on a short journey.