Also, GEDCOM doesn't accept two-principal tags except for recognized "family" tags, such as marriage and census... maybe Michael can check.
The following is probably more detail than you or Jim want, Terry, but I thought I would post it here so other users may find it in the future.
Unfortunately GEDCOM is at the same time more limited and more flexible in its capabilities than that. Any TMG event with two Principals cannot be exported to GEDCOM if those Principals are not married, regardless of whether the type of event is recognized by GEDCOM. Family (i.e. two-Principal) events in the GEDCOM family record can only be shared by the individuals if they are also designated as explicitly married by HUSB and WIFE entries in the family event. Even if the two Principals are married the event is exported as a family event, not an individual event. This is the explicit design of the GEDCOM 5.5 specs. Only family events are recognized by GEDCOM specs as capable of having two Principals, all other GEDCOM events must have only one Principal.
If they are married, GEDCOM defines the following as "family" events (with its event code): Annulment (ANUL), Census (CENS), Divorce (DIV), Divorce filing (DIVF), Engagement (ENGA), Marriage (MARR), Banns (MARB), Marriage Contract (MARC), Marriage License (MARL), and Marriage Settlement (MARS). In addition, GEDCOM also defines a generic custom family event type (EVEN) which will be followed by the custom name of that event (TYPE). Therefore any TMG event with two Principals can be exported to GEDCOM as a family event if they are married. But if a TMG tag has two Principals, and they are not married, the entire tag is excluded from the GEDCOM output. This, and no ability to link witnesses, are probably the two most limiting restrictions of GEDCOM. However other TMG data can be lost/excluded on export to GEDCOM such as non-traditional relationships, non-primary relationships, relationship notes/sources, parent(s) of unknown sex, unwed parents, exhibits, research tasks, and sources of sources, among others.
GEDCOM is very appropriate for exporting and sharing the basic BMDB data of a genealogy line of parents and their children, but is incapable of including many of the features and data now in modern genealogy software programs like TMG.
Hope this information is helpful,