Dear all,
I would like to use the light version of the Ubuntu font both for text and for text in math environment. The list of fonts is the following

mtxrun --script fonts --list --all  | grep ubuntu
ubuntu                               ubuntu                            /home/flavien/.fonts/Ubuntu-R.ttf
ubuntubold                           ubuntubold                        /home/flavien/.fonts/Ubuntu-B.ttf
ubuntubolditalic                     ubuntubolditalic                  /home/flavien/.fonts/Ubuntu-BI.ttf
ubuntucondensed                      ubuntucondensedregular            /home/flavien/.fonts/Ubuntu-C.ttf
ubuntucondensednormal                ubuntucondensedregular            /home/flavien/.fonts/Ubuntu-C.ttf
ubuntucondensedregular               ubuntucondensedregular            /home/flavien/.fonts/Ubuntu-C.ttf
ubuntuitalic                         ubuntuitalic                      /home/flavien/.fonts/Ubuntu-RI.ttf
ubuntulight                          ubuntulight                       /home/flavien/.fonts/Ubuntu-L.ttf
ubuntulightitalic                    ubuntulightitalic                 /home/flavien/.fonts/Ubuntu-LI.ttf
ubuntumedium                         ubuntumedium                      /home/flavien/.fonts/Ubuntu-M.ttf
ubuntumediumitalic                   ubuntumediumitalic                /home/flavien/.fonts/Ubuntu-MI.ttf
ubuntumono                           ubuntumonoregular                 /home/flavien/.fonts/UbuntuMono-R.ttf
ubuntumonobold                       ubuntumonobold                    /home/flavien/.fonts/UbuntuMono-B.ttf
ubuntumonobolditalic                 ubuntumonobolditalic              /home/flavien/.fonts/UbuntuMono-BI.ttf
ubuntumonoitalic                     ubuntumonoitalic                  /home/flavien/.fonts/UbuntuMono-RI.ttf
ubuntumononormal                     ubuntumonoregular                 /home/flavien/.fonts/UbuntuMono-R.ttf
ubuntumonoregular                    ubuntumonoregular                 /home/flavien/.fonts/UbuntuMono-R.ttf
ubuntunormal                         ubuntu                            /home/flavien/.fonts/Ubuntu-R.ttf
ubunturegular                        ubuntulight                       /home/flavien/.fonts/Ubuntu-L.ttf

I tried a script that I used before for Maven pro through,

\definefontfeature[default][default][script=latin]
\definefontfamily[mainface][sans][ubuntulight]
\definefallbackfamily [mainface] [math] [ubuntulight] [math:lowercaseitalic] [force=yes]
\definefallbackfamily [mainface] [math] [ubuntulight] [math:digitsnormal]    [force=yes]
\definefontfamily     [mainface] [math] [TeX Gyre Pagella Math]
\definebodyfontenvironment [11pt][a=12pt,b=14.4pt,c=17.3pt,d=32pt,interlinespace=13pt]
\setupbodyfont[mainface,11pt]

but it does not work (it is ok if I use ubuntu instead of ubuntulight).
Thanks for your help,
F.