What to consider before you buy
Your seat is one of the biggest influencers when deciding screen height. Many change the seat to improve the overall comfort for long rides. While others simply need to improve their ability to comfortably reach the ground on those infrequent stops around town.
Whatever the reason to make a change in your seat remember the relationship to the screen will also be affected. Make sure to acquire and install your seat prior to checking for your screen height.
With all of the above completed you are now ready to choose the correct height.