Address fancyhdr warning about too small 'headheight'

Without this, I'm getting a warning from fancyhdr on every page, making all other messages drown completely in the fancyhdr noise.

preamble.tex

@@ -6,6 +6,7 @@
 \usepackage[english]{babel}
 
 \usepackage{fancyhdr}
+\setlength{\headheight}{10.5mm} % Address fancyhdr warning about height being too small.
 
 % The general view was that parskip without indent was most readable, so use it
 \usepackage{parskip}