You mean the width of the theme? I would change it but alot of people have smaller screens so it would be a problem for them as I tried it in the past.
I usually like recommended widths of about a maximum of 850px but a width of 85% fluid width but I think the style as it is is rather nice and does not need changing.
Yea I tried it in fluid, and it was all cramped for people with small screens, and when made its width fixed and larger, the people with the small screens had to scroll right and left to see everything. So thats why I have it set to this as its perfect for all screens.
I solved that problem with this CSS code, that way everyone was happy. Code: min-width: 850px; width: 85%; I don't know where that would have to be placed on Xenforo styles though