Cool thanks for that - I actually found another way that sets it from the server side 
You can add options to /etc/loolwsd/loolkitconfig.xcu. It seems that anything that works in the desktop version’s preferences can be added in there and they take effect! The desktop file is ~/.config/libreoffice/4/user/registrymodifications.xcu and contains a million options. The LOOL version is very slimmed down with only about 5 options by default.