The best answer, if you have the money for it, is an adjustable seat and desk.
Both need to be adjustable up to operator height (the height of a bar in a pub). So, in the mornings you might sit low at normal office desk height. Come the afternoon, you raise both up high and sit at that height. This means you are maximising the difference between various seating positions, throughout the day.
Unfortunately, strong and easily adjustable desk don't coem cheap. But, if the demand increases the price should fall.
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