Well, just by chance my copy of Brew Like a Monk finally arrived this week. Apparently, some brewers do use honey in tripels.
I'm not quite sure what you mean by secondary. You'll probably be better off adding it after the main fermentation has taken place as otherwise you'll lose most/all of the aroma (though you might anyway). Just add it after a week in primary or if you rack to secondary then that's a good time.