Doing dovetails or box joints on large pieces with a table-mounted router can be a hassle, since the large piece needs to be held firmly in the vertical position.
I'd suggest considering a bench-mounted 24" jig, used with a hand-held router. Leigh or Porter Cable are good, albeit expensive, candidates. How often you might use the jig will help determine whether the investment makes sense.
With a bit of practice, you could also simply hand-cut the dovetails, of course.
Last edited by Ralph Barker; 01-27-2011 at 12:07 PM.