Ive had the GTD for nearly 1 year and have just found out that the centre armrest height is adjustable!
Im a bit slow and this may be obvious to everone else, but new to me

By opening the lid/armrest just a bit there are 3 ratchet positions, opening the lid fully and closing again resests the position to fully closes.
At full height and fully extended it is a much more comfortable position for long motorway driving.