\DeclareErrorFont {<encoding>} {<family>} {<series>}
{<shape>} {<size>}
Declares <encoding><family><series><shape> to be the font shape
used in cases where the standard substitution mechanism fails
(i.e. would loop). For the standard mechanism see the command
\DeclareFontSubstitution above.
The font specification for
<encoding><family><series><shape>
must have been defined by \DeclareFontShape
before the \begin{document} is reached.
Example:
\DeclareErrorFont{OT1}{cmr}{m}{n}{10}
\fontsubfuzz
This parameter is used to decide whether or not to produce a terminal
warning if a font size substitution takes place. If the difference
between the requested and the chosen size is less than \fontsubfuzz
the warning is only written to the transcript file. The default value
is 0.4pt. This can be redefined with \renewcommand, for example:
\renewcommand{\fontsubfuzz}{0pt} % always warn