No change in speaker height at all actually, when you are setting up your receiver with the SPL meter it might require a little boosting to level match the rear surrounds, but that isn't a big deal. Also, you will want to ensure proper distances input in the receiver as well, but again that just requires a tape measure.
Just keep everything at the same height and you will be golden
.
Also, with a room like that you should think strongly about room treatments and possibly laying carpet on the floor with thick padding, if possible.