Hotep,
i think it largely boils down to personal choice if you want to use 3 monitors in portrait mode, try it. there are some strong arguments for it, for ex that you can see your rear view mirror, scenery/sky ahead, and instruments all at the same time. somebody on the ubi forums was a strong proponent of this and used his 3 monitors that way
note: you can easily setup the config ini to use monitors in portrait mode for il2, it works well
arguments against using portrait mode for 3 monitors:
1) lcd screens are designed to be viewed in a particular position to provide best video quality, and for most current widescreen lcd's this means using them as intended in landscape mode (it has to do with pixel orientation, the image wont be as crisp and clean in portrait position)
2) peripheral vision is what is mostly lacking in flightsims, increasing it makes a big difference in improving immersion. imho it is better to see 2x more on either side of you then "waste" screen space by constantly seeing your instruments and in-cockpit objects (except the mirror of course)
it will however come down to personal choice, for me the peripheral vision is more important
