[GNC] two instances on different books

[Brook Milligan]

Is it safe for a single user to run simultaneously two different instances of GC on two different books?

If so, what settings are shared between them and therefore must be the same?  I can think of all the general settings, which mostly seem to be preferences about overall features like whether or not to use formal or informal names.  I would expect no conflict as these are preferences of the individual GC user and stored within a user-specific directory. Have I missed anything here or misinterpreted this?

However, I can think of one preference that is not like that: the root directory for associated documents.  I believe this is also a user-specific setting not a book-specific one (please correct me if that has been changed, which I eagerly wish for).  If so, then the two instances are forced to have documents in the same directory, something that might or might not be appropriate.  Are there any other settings like this that would interact (possibly poorly) between two distinct instances of GC?

Thanks for your help.

Cheers,
Brook