Is a "fluid" Header image possible?

I searched the forums and found an old post from last year about this http://forum.bytesforall.com/showthread.php?t=301

However the code mentioned to be changed looks different now and i'm guessing that is because of updates and what not. Just want to make sure that the majority of it is still relevant. Or maybe there's a better/easier way to do this now.

I am currently using the style, "Overlayed Blog Title/Tagline Style" to display that info and then center it within the header(which is awesome!) and am hoping that doing the above would also keep this the same and center it non the less.