The xmod file suggests the data is stored as model-specific:
...but Monarch picks up these values from the registry.
Some organisations impose a standard - network paths, default locations for saving models etc, which is put into the registry for every machine when Monarch's installed.
Can you edit your registry?
Just to qualify Olly's post a little.
I think the initial Font default is always picked from the registry as the default when a new model is created but if you change the font information to something specific it will be stored in the model when it is saved.
At least that is what I would expect. It might be nice to have the options to set new defaults at the base level for a new model. Editing the registry is not a well recommended task even for those will access allowed!