Put the question "is it passable" first maybe easier, since this is not a common bid. Assume you had no agreement on this sequence before. This 4H is passable because: 1. You have clear 4C/D as forcing slam try bid, with no confusion 2. Two possible sceneries you can pass a) 4H for a safer place, with more high cards on majors, w/o good D stopper :( Mild slam try, 3-2-3-5, w/o D control I think 4H for a) is more useful, likely 13-15pts, 3-2-3-5 or 2-2-4-5.