Current Dolby specification is 110-120-deg and ear height. It used to be 1-2 feet above ear height before object oriented formats arrived, now it's actually spec'd at ear height. I disagree with that specification though, I think it should be a bit above so that it clears furniture and other heads.

Dolby virtual 5.1 speakers setup guide

It's hard to tell from your photo, but if you're close to the wall like it seems, then I'd probably mount them so the tweeters are about 1ft above ear height and I'd probably angle them a little off axis, sort of firing at each other.

If they are really close to your head and on axis it can be distracting and very localized, where with 5.1 imo it's better to be a bit more diffused to fill in the rear and side gaps of information (this is why dipoles were popular with 5.1).

Mount them on a rotating bracket so you can play with a bit bit after they are mounted, but, I'd do 1ft above ear level or whatever height gives the tweeter a clear line of sight to everyones ears without any obstruction.