Wang
I think that Capt Claret knows what he is talking about here. "Pretty close" (as you put it) is about 36 ft or 11m, and with the airspeed taken into account it is difficult to see a problem. Now take a look at the A340-600 (see link below), but it must also have met the stringent certification requirements. Are there any 744 guys able to tell us of any restrictions on the dump procedure ?
http://upload.wikimedia.org/wikipedi...mpA340-600.JPG