Fallback text in header if overlapping occurs

I'm currently working on several projects, where the authors are read from a textfile. I'm also displaying the authors in the header using fancyhdr. This works great if there are just 2 or 3 contributors, but if there are more, the text starts overlapping.

The overlapping is also dependent on the document title, which is shown the left.

Is there a way to detect whether the text overlaps, and if it does, use a fallback text (an URL) instead of the authors instead?

Header specification looks like this at the moment:

\usepackage{fancyhdr} % Fancy headers

% Capture title and author
\makeatletter
\let\Title\@title
\let\Author\@author
\makeatother

\pagestyle{fancy}
\fancyfoot{} % Clear all footer fields
\fancyfoot[CO,CE]{Page \thepage}
\renewcommand{\footrulewidth}{0pt}

-

\makeatletter

This will use <whatever> if there's not at least a quad of space between the title and the list of authors.