Okay, I posted this at vb.com hoping for some developer comment and basically got fobbed off over here ...
So ....
I was under the impression that the new Data System should allow you to add new fields to tables, and use them without the need to hack the actual files.
However, I can't find a way to have a new field in posts without getting an SQL error when creating a new thread. New replies are fine.
The reason appears to be that the do_set() function in the Thread_FirstPost Data Manager defaults to assuming that any fieldname it doesn't know is a thread field, not a post field, therefore generating an unknown column error in the thread table when it tries to insert it - and I cannot see any way to fix this without hacking the class file, which rather defeats the object of trying to do it all by hooks.
Is this a bug / design problem, or have I overlooked something ?