Ah, that's a case I had not thought about before. I've never touched oid columns and similar magic things. So these have to be selected (and retrieved on insert), but not written to? It should be easy to add a new slot flag to do just that. Any chance you can do this yourself? (The relevant code is all in postmodern/table.lisp, but contains some weird MOP-related work-arounds.)
Best, Marijn