Correct method to add extra fields to threads?

[Razasharp]

I am thinking about adding some extra fields for threads and wondered what you all thought was the best way to go about it.

Should I add the fields to the existing thread table, or create a new table for these fields?

There will be around 6 or 7, however, not all forums will be using them, actually just a handful. So for the majority of threads they won't be needed. Also, the info in these extra fields won't even show on showthread - they are being added for internal use only, hence their data will be called in a custom script. (Although they will be added/updated by mods or admin via edit thread)

Most of the hacks here add them to the thread table, however, some hacks like GARS create a separate table. Hence I wondered what you thought the best, most efficient method is.

Also, is the information in this thread still current?