Twilight 600 control advice please

[Feanor]

I've been plotting the Twilight 600 in Google Maps, and it's coming out under-distance.

Here's what I've plotted:
https://goo.gl/maps/VBXC1RksJe12

In summary ( Controls as I understand them in BOLD ):

South Queensferry, Crieff,
Aberfeldy,
Crianlarich,, Glencoe,
Corran Ferry,
Acharacle, Glenuig,
Lochailort, Gelnfinnan,
Fort William,, Ballachulish
Oban, Tyndrum, Crianlarich,
Lochearnhead,
Callander,, Br of Allan, Fallin, Grangemouth,
South Queensferry

It comes out at 589k, which is quite a bit under-distance.
Am I going the Wrong Way somewhere, or is the route historically under-distance?

I can always push the start / finish controll back to Edinburgh to make up the shortfall, if necessary.

EDIT:
Looks like there's a control at Kelty.
That seems to pretty much nail it down.

http://www.bikely.com/maps/bike-path/Twighlight-600km