Rather then steal certain other threads, I'm creating a new thread based of others. How much dressage do you think one needs to jump? I've never taken a single dressage lesson (and don't have any opportunity to) However, although it's not called dressage at my barn, I do take usually one flat lesson a week, working on bending, leg yields, circles, and especially getting my big boy to work underhimself. Then, my other lesson is 15 mins flat work, 15 mins jumping. I'm only jumping <2'6" on my 16'3" horse, and will be doing so for several months. Even after that, I doubt I will jump over 3ft.
My opinion is that this is plenty. I don't think people need a professional dressage trainer if they ever want to jump, I think they need a trainer who works on the flat, and the rider has to be wiling to practice outside their lesson, not just excersize. Also, form, striding, and carriage should be valued over jump height. With that, I think jumping is no problem, IMO it's not reasonable to say a horse and rider should be 2nd level dressage just to jump. What do you think?