fop 1.1 servlet ignores my custom TTF font

Respectable, I've been trying many ways to solve this, following online 
manuals, reading forum posts etc., but I miserably failed. I'm no Java 
expert.

Environment is Linux, Java is 1.6.07, fop is version 1.1
To make sure I'm not stuck with some cache, everytime I have stopped 
Tomcat, remover webapps/fop* and put the new fop.war into webapps/, then 
re-run tomcat.

I have some fonts that I must use in the PDF renderer (FO to PDF 
transformation), let's say I just have one that is 
/opt/fopTest/fonts/Ocrb.ttf

After trying some recipes found on the web, like retouching fop.xconf 
before compiling or where I just put the fop configuration file 
somewhere... nada.
Currently I have modified 
src/java/org/apache/fop/servlet/FopServlet.java this way:

     public void init() throws ServletException {

             this.uriResolver = new 
ServletContextURIResolver(getServletContext());
             this.transFactory = TransformerFactory.newInstance();
             this.transFactory.setURIResolver(this.uriResolver);

             // Ubi: here or in position POS-ALPHA,
             // the effect seems to be the same (fonts not found!)
             try
             {
                 File userConfigFile = new 
File("/opt/fopTest/Ubi.fop-config.xml");
                 this.fopFactory.setUserConfig(userConfigFile);
             }
             catch (Exception exc)
             {
                  // I don't see the point in catching this one, should I?
             }

             this.fopFactory = FopFactory.newInstance();
             this.fopFactory.setURIResolver(this.uriResolver);

             // POS-ALPHA

             configureFopFactory();
         }


and /opt/fopTest/Ubi.fop-config.xml just contains


     <?xml version="1.0"?>
     <fop version="1.0">
       <renderers>
         <renderer mime="application/pdf">
           <fonts>
             <!-- Ubi: try this one... -->
<directory>/opt/fopTest/fonts/Ocrb.ttf</directory>
             <auto-detect/>
             <!-- Ubi: (the previous was apprently insufficient for the 
servlet)
                     ....try this one, too. See 
https://xmlgraphics.apache.org/fop/1.1/fonts.html#register -->
             <font
                             embed-url="file:///opt/fopTest/fonts/Ocrb.ttf"
                             encoding-mode="auto">
                             <font-triplet name="OCRB" style="normal" 
weight="normal" />
             </font>
           </fonts>
         </renderer>
       </renderers>
     </fop>


By running tomcat with strace, I see that file 
/opt/fopTest/Ubi.fop-config.xml is actually read, but the font OCRB is 
not found when invoked (logs/catalina.out):

     WARNING: Font "OCRB,normal,400" not found. Substituting with 
"any,normal,400"


On the command line, this one works, instead :

java -cp build/fop.jar:lib/xmlgraphics-commons-1.5.jar:<the usual 
lib/*.jar files> \
         org.apache.fop.tools.fontlist.FontListMain \
         -c /etc/PeS/var/FOP/Ubi.fop-config.xml \
         /tmp/test2.pdf

and the OCRB font appears in the PDF.

So, what am I doing wrong with the servlet???
Is there a bullet-proof way to exploit fonts, possibly with the standard 
fop servlet (without writing code)?
Otherwise, how can I quickly debug/inspect the issue?

Thanks a lot

    Ubi