I searched high and low where to set the proect dimensions as millimetres (it defaults to centimetres). You can set overall dimensions easily enough under Preferences, but changing the project to millimetres forever eluded me.
Finally I gave in and contacted the most excellent Maxon support people. Here is there answer…
To use own startup project settings or viewport settings you should create your own template.
This is a c4d file used to open a new file with specific settings already.
You just have to open a new file setup all your settings for a default new scene and save the file as “new.c4d” or “template.c4d” into your Cinema 4D userfolder.
All information about this topic you can find in our documentation:
Hope this helps someone!