TV Mounted above fireplace mantel - neck strain?

All of mine are at eye level except office.
There, top shelf = neck strain.

Not a fan or tilt and lean. Straight ahead. Wherever you put it, watch out for glare and reflections.

I dislike too high.

also consider proximity to speakers, l/r imaging height, and, where center speaker is to anchor the dialog to the screen.

I have found, directly below the monitor works best for center.

I have been able to blend this into several situations

https://www.ebay.com/i/233696110070?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&am...

never considered getting anything different.

Stand up, relax, and notice where your eyes normally look. You’ll notice that our resting eye position has a field of view approximately horizontal with our forehead, downwards. Approximately.  If you say you are looking straight, it's not actually your resting point.  Your mind is just conscious of it and forcing it ahead.  Relax  your eye muscles and your view will shift down. 

That is, our eyes are naturally looking below horizontal. This is why ergonomic guides suggest the top of your PC monitor be at forehead level, and why people who raise up their monitors have an S shaped neck. They hunch over and raise their heads. Bad posture!!

So, if you plan on watching in a recliner, up is good. Otherwise, having the top of your TV about the level of the top of your head is best.

Evolution involved walking and looking down a lot. Tv viewing angled slightly down makes sense.  This creates a huge problem for center speaker placement as well.  
If you have outstanding fronts you can do without a center.  Use stereo for tv viewing and sound seems to come from center anyway.