I have been on the 'Immersion' wallet cruncher for nearly 10 years now and each step I take put me closer to never retiring!.... but I just can't afford to go to the real track 3 or 4 times a week, so in that respect and in comparison, it's quite cheap!
With one small screen, using the mathematically correct FOV is very difficult to get used to without something like TrackIR (caveat: there are other head tracking systems available) to allow you the freedom to see more at the right perspective... and that's all it is, the right perspective and what your brain will accept.
I'm a big fan of doing things the right way, but not to the point where it spoils my enjoyment, I have been called pedantic, but I think I'm just picky!
I have been on a journey with FOV and when you add the means to look around you naturally, it makes a lot more sense to everybody. I don't use TrackIR now but used to with a single screen and also when I went triple 24"... I now race on a 170° 26.5"radius 84" (diag) 21:9 screen from a nominal distance of 26.5" and the ratio to real life is 1.09:1 so almost there for a 1:1 mapping, my vFOV is 64° and hFOV is about 111° and the immersion is about as close as I can get considering the just under 1mm pixels.
I'm just about to retire my screen and PJ to go for a 55" curved 4K TV to get the picture sharpness back and to add the detail back in as 1920x822 is no good for my 'picky' need as a graphics whore! If I lose too much immersion by doing this, then I'll just stick the TV in the living room and pop my PJ back on the wall
My point is.... what matters is my enjoyment, not the technical aspects of whether it is mathematically correct. If you are 'picky' like me, then this matters somewhat and even at nearly 1:1 with a life size windshield for me to look through, sometimes I have to tweak an extra 5° as the in car view is not correct in game to make it feel right.
I didn't publish the FOV calc for people to argue about it and it's use, it's there so that you don't have to try to figure out arc tangents and sines etc.... e.g. "do the math", but only as a guideline. I have been inspired by many a fellow sim-racer over the years, my first adaptation was in the mid 1980's when I stuck a recaro seat on an office chair base and made a pedal set and wheel from the guts of a joystick to play 'Stunt Car Racer' on the Amiga 500... in cockpit view.. so when I saw ZeosPantera's explanation of FOV on one site or other I jumped in with both feet!
At the end of the day, do what makes you happy, but be wary, happiness in sim-racing is darn expensive if you let it take hold!
All the best,
Paul (a.k.a. MrPix)
http://www.projectimmersion.com