So there is a spec. It says that rear speakers, meaning the surrounds should be at the same height as the mains, OR no more than the mains heightX1.25. So the mains tweeter at 40”, would give you 50” max for the surrounds. But as TLS guy mentioned, you should go slightly higher if you need to clear seat backs, or other listeners
As shown above. I had to go H2x1.55 to clear a switch out.
I’ve also seen that whatever distance you raise the surrounds, you should move the tops inward half of that distance to maintain adequate spacing between the surrounds and tops.