TV Mounted above fireplace mantel - neck strain?

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.  

center is a phantom created by l/r in 2 channel system, and when using home theater in 2 channel stereo mode.

however, using dolby 5.1, other surround ...., the center channel is given to the center channel, it is not the same, you want a properly located/blended center speaker, and it must be close enough to anchor it's output to the screen.

if using a sub in a home theater, when using only 2 channel mode, you want all the bass to go to the front, that is why it is important to get good, 'fuller' range mains, and understand your av receiver/sub/spkr hookup yourself, or have a friend nearby.

No more neck strain from watching TV 

https://mantelmount.ca

MantelMount not only offers tilt and swivel, but also allows you to easily pull the TV down off the wall and position it at eye level in front of a fireplace. And you can just as easily push it right back up. - patented technology and full range motion

Mantelmount reviews are not stellar. Problematic.

i think I may just position tv in front of unused fireplace.  It may look fine.  I hate having to pull it down all the time and often it will be left lowerEd and look like crap when not I use.  When lowered you see the bracket mechanism which sucks.

center speaker will be close to floor level and angled upward. Stupid stupid fireplace, which really can’t be removed. 
All this to get a larger room to improve overall sound where dens can be too damn small for high end speakers.