TV Mounted above fireplace mantel - neck strain?

Spoke to electrician today and he said mounted tv extended out diagonally to shift set lower for viewing are not advisable.  He said just mount it and angle set down.  He didn’t seem concerned about higher placement.

curious what people are doing out there.  
As a decorating motif it's a cliche.  As a practical matter I know people who say it works fine.
Depends on your situation. If you're watching leaning back so your head is at a comfortable angle then probably fine. You just want to avoid looking up, as anything the least bit uncomfortable for a short time can annoy over time. Unless you get used to it. So I would put something there, sit and pretend and see how it feels. 

Neck strain or eye strain (having to look ’up’ from straight ahead) will be a function of screen center height, viewing distance, and viewing angle(any upward angling of the eye).

I don’t have my big screen over the fire place, but I do have it wall mounted because of room constraints.

I did some calculations for my room and got the screen center set to give zero eye angle up with my comfy couch. No neck strain or eye strain.

Depends. If you are close and the screen center is high up - they yeah - it could be an issue.

I won't get into WAF or other decorating preferences.  Strictly from a 'human factors' standpoint - it can be done.
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

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.  
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

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

Yes, but if possible, tilt it towards the listeners.  This can improve intelligibility by reducing floor bounce and putting the listener in line with the tweets.  If your main speakers are on axis but center isn't, the center will sound dull by comparison.
In the early days of the ARPA net I developed a strange neck problem.  Some of the diagnostic procedures were quite unpleasant and all unproductive.  Then I read a Bell Labs study of monitor placement, lowered my monitor from a shelf above my desk, and never experienced the neck problem again.  Needless to say that experience has guided the placement of our TV and projection screens -- line-of-sight slightly down.