Problem with 'feyn' package for 11pt font size

Question

I need to draw several Feynman diagrams and I found the feyn package suitable enough for this purpose. I use MiKTeX to compile the tex-file. The problem is that for some strange reason it does not accept 11 pt font-size? I say strange, because the 10pt and 12pt versions are perfectly executable, and the difference between them and the 11pt-module is just in the values of some arguments (arrow width, loop radius, etc.), which shouldn't cause any compilation problems...

The exact mistake description, which I get, is:

! I can't find file `cmr11'.

l.33 input cmr11

            ;^^I^^I^^I% ...but miss out the `generate roman'

Please type another input file name

! Emergency stop.

l.33 input cmr11

            ;^^I^^I^^I% ...but miss out the `generate roman'

Transcript written on feyn11.log.

miktex-maketfm.exe: Windows API error 2: The system cannot find the file specified.
miktex-maketfm.exe: Data: feyn11.tfm
! Font OMS/feyn/m/n/10.95=feyn11 at 10.95pt not loadable: Metric (TFM) file not
  found.
<to be read again> 
               relax 

 l.99 \setbox0=\hbox{$\FeynSpaceChar$}
?

Here is an example with the (working) 12pt font-size:

\documentclass [12pt]{article}
\usepackage{feyn}
\begin{document}
    $\Diagram{ fdA & & fuA \\ & g & \\ fuA && fdA }$
\end{document}

Answer 1

Here is feyn11.mf:

% Feynman diagram font, 11pt display size, release 0.3.3, 2009 October 8.
%
% Copyright 1991, 1994, 2001, Norman Gray <norman@astro.gla.ac.uk>
% Mercurial revision 204fc9a2e560, 2009-10-08 12:56 +0100

font_identifier "FEYN"; font_size 11pt#;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% First the base size

module# := 11pt#;

% phfudge is ... what?!
phfudge# := 0pt#;       % must be, for \Diagram macro

linewidth# := 0.85pt#;      % pen width
thinlinewidth# := 0.55pt#;  % thin pen
bigarrow# := 6.5pt#;        % size of arrows
littlearrow# := 4.5pt#;
blobr# := 7pt#;         % radius of blobs and crosses

on_math_axis := 1;

% We want the roman digits from the corresponding cmr font, and that's
% all.  Therefore, we don't want to obey the `generate' command in
% cmr??.mf.  To do this, we read in cmbase, and then set generate to
% gobble its argument. 
def gobble primary g=enddef;    % gobbles its argument
input cmbase;           % Read it explicitly, rather than
                % implicitly within cmr10
let generate=gobble;
input cmr11;            % ...but miss out the `generate roman'

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% To business....

input feyn;

end

There is no cmr11.mf file in the standard distribution of the Computer Modern fonts, so running Metafont on this file will result in the error

! I can't find file `cmr11'.

l.33 input cmr11

unless the sauter package is installed too, which is able to supply interpolated versions of the files in the Computer Modern font distribution.

For MiKTeX the package is listed at http://miktex.org/packages/sauter so it can be installed with the wizard. For TeX Live it is

tlmgr install sauter