I will be using a 21" computer monitor... and plan to have it horizontal.... (the normal way for the monitor...)
one thing to keep in mind is... if you're using a tv or a computer monitor... and you want to mount it so it stand on its side....plz keep a few things in mind....
- some of them have their main heat exhaust on top (by design)... (like circuit board will be vertical, .... more heat vents on top... etc.)
- some monitor / tv might have color shift if you put it aside for a while... (like 1/2 hr or so....) and you might have to degauss it....
- make sure you mount it where it is secure.... cos if they're not designed to be mounted vertically... and you just screw it in.... places where you're leveraging the weight might not be strong enough....
these are a few things I learned from this site...

but as long as you watch out... it should be ok....
there are quite a few success cab with vertical mount monitors....
good luck....
