I've been researching online, and there is slot of conflicting advice as to how high the tv should be mounted based on seating eye level, distance etc.

Any thoughts or suggestions based on the following:

Tv size (diag): 82 inches
Tv height: 40.5 inches
Eye level viewing height: 42 inches
Viewing distance 144 inches (12 feet)

How far off the floor should the bottom of the screen be?

I've always enjoyed have my eyes at the center of the tv screen and for my big screen I tend to like my eyes roughly in line with the 3/4 screen height mark.
I have both on the bigscreen actually, the second row/seat is raised.
Just my current preference.

I'm trying to balance eye level and not being too low to the floor.
It's a large screen, no 2nd row for seating, so If I were to mount at 3/4 screen height for eye level, the bottom of the screen would be only 12 inches from the floor.

I'm looking at 27" from floor, about 38% screen height at eye level. Leaves room for center channel placement options, etc.

In theory, the most comfortable viewing height would be a height that minimizes the extent possible neck and eye strain. Therefore, you would want the center of the screen to be roughly at eye level. People who mount TV's above fireplaces always baffle me unless you have a recliner and your sightline is angled up...

So, in ideal conditions, for an 82" TV, the bottom of the screen would be about 21.25" from the floor assuming an average 42" eyelevel seated height... this doesn't give you a lot of room for a center speaker or entertainment unit.

WAF and aesthetics can also come into play. I like my TV as centered as much as possible between floor and ceiling... Assuming an 8' ceiling, that would mean mounting the TV at about 27.25" above the floor. The further you sit back, the less extreme the 6" has on your viewing angle so this would be quite acceptable.

http://www.sanus.com/en_US/heightfinder/results/samsung/82/UN82MU8000/vxf220-b1/centered/42/0/in

I think you answered the baffling part in the succeeding sentence. Not everyone has an ideal setup. Most 'new' homes i've seen all have a family room off the side of the kitchen (think open concept) and inevitably there is a fireplace (gas) with some wall decor for books and yep, a tv above the fireplace.
Blame the home designers, not the home owners.

That being said, we have a huge wall on our main floor and knew at some point, not being able to put any art on it in a meaningful way next to tv, meant just getting a really large ass tv to try and fill enough of the space to make the wall look reasonably filled.
So we bought a 65".
https://www.sony.com/electronics/televisions/xbr-x900e-series

It is located about 2/3s the way up the wall to accommodate speakers and a rack underneath. The bottom edge sits at 52" off the floor and hence middle of the screen is way above 42". However, we also sit about 15' back from the wall.
There really isn't any neck strain to speak of as the angle of view declines with distance away from the screen. It works just enough.
Now if we were sitting 10-12' away...

But why doesn't the home owner take the queue from Apple and have the courage to mount the TV infront of the gas fireplace so it is the correct height and have the bonus of a fire like surround glow around the outside edges of the TV. That is until the TV overheats and actually catches on fire.. but that could be cool too.

Taking another cue from the laptop world you could run heat pipes from back face to front face around the edges of the laptop, so heat could radiate from the front instead of all going into the TV.

For those with a TV over a fireplace, or some other "thing", look into a "mantle mount". It's a great option. I just installed one, and it really helps. Not cheap, but worth the cost.

So, I compromised a bit, the bottom of the panel is 28' from the floor, enough room for the on wall VP 180 with about 16 inches to spare below that space. it is comfortable to watch with no strain of any kind.