Is there a recommended height range for the Theatre soundbar
When Geoff Martin was asked long ago about how BeoLab 18s could be located properly, given that the tweeter acoustic lens was not on a level with the listener's ears, he said the crossover and sound profile had already been adjusted for a seated listener to get the most even frequency response. (I believe he even named a seating distance and a height measurement.) Your best course of installation would be to assume that the same has been done for the Theatre. Also, the Theatre is designed to calibrate itself based on you placing its microphone at your listening position, so -- theoretically -- it can make up for unevenness, in each channel individually.
Therefore, adjust the screen the best you can, so you aren't craning your neck or slouching to get the maximum immersion, then let the Theatre do its work! Typically, that means mount your television so that in a seated position, the viewer's eyes line up with the middle of the screen, then mount the Theatre hard up against the bottom edge, as the B&O stand does -- that's assuming it's a LG G-panel or thinner and free-standing. Otherwise, mount it a few inches lower if a thicker screen blocks the drivers. The closer to the screen, the better the sense of location from the center channel,... BUT... for example, a Sonos soundbar recommends at least 4 of distance so the upfiring drivers can radiate before reflecting off the screen, and also recommends at least 1 foot from the wall.
Does the Technical Sound Guide really not address this issue? May be ripe for a 0.1 edition!