Hey Adrian,
As others have pointed out, center-channel placement always comes down to performance and freedom from audible coloration. In my case (a 50-inch DLP Samsung rear-pro), my center sounded much better on top of the Samsung than below it. I had to buy a rickety shelf to position the center above the TV. It looks stupid, but it sounds good.
Actually, in my experiments with center-channel placement and listening tests, the center sounded best of all on its own dedicated stand out from the TV and free of any boundary effects. But that's not practical in my room, or in most rooms.
So you accommodate to what is practical and what sounds reasonably good.
Regards,
