if possible try align the surface of your centre channel to the surface of your LR speakers, the idea is your LCR channels sound wave should arrive at your ear at the same time with as little adjustment from your AV amp as possible.
Are you talking about ITU-R standard? (see link below) http://www.post76.com/wordpress/?p=6633
In this case all sound wave arrive at the same time and little adjustment is required.
But I'm using Dolby and DTS setting. In my case the LCR aligned on the same plane. But the distance to my ears are different. In this case I have to adjust the time delay (distance) in my Amp.