jtr
(1) Thanks but they're not pure cotton
(2) always - I get home quicker that way
(3) will try to remember that in future - whilest on the subject have just found a book describing the differences for the 400, which includes "a new stabiliser tank holding 3,300 US gallons, which should give 350nms extra range". I guess my definition of approximate may be a little bit loose, but then aircraft manufacturers ranges are notoriously approximate themselves!
(4) I stick by my answer to the original question - it's trim/load versus range for the freighter and good luck for the interview.