Specifying proportional numbers when using Libertine with pdfLaTeX

Question

If I use the Libertine fonts from within XeLaTeX I can specify the use of proportional numbers/figures by including it as an option when I set the main font like so:

\setmainfont[Numbers={Lining,Proportional}]{Linux Libertine O} 

However, I'm also interested in being able to using proportional numbers when using pdfLaTeX. Below is a MWE that shows one way to do this. My "solution" seems awfully ugly though. Is there a better way to accomplish this?

\documentclass[12pt]{article}
\usepackage[T1]{fontenc}
\usepackage{libertine}

\begin{document}
% this seems necessary to get proportional numbers in Libertine
% when using pdflatex. Comment / uncomment to see the difference    
\usefont{T1}{fxlf}{m}{n}\selectfont    

I would like the following numbers to be proportional so that 11, 
doesn't take up as much space as 17. See what I mean?    

\end{document}

Answer 1

As Mico has commented, "[t]here seems to be no ready-made option at the package's load time in order to achieve this effect." However, if you want to put your specification in the preamble, you have use \AtBeginDocument{\usefont{T1}{fxlf}{m}{n}\selectfont}. Another possibility is to redefine libertines internal commands:

\documentclass[12pt]{article}

\usepackage[T1]{fontenc}
\usepackage{libertine}

\makeatletter
  \def\libertine@param{fxlf}% comment / uncomment to see the difference
  \def\biolinum@param{fxbf}
\makeatother

\begin{document}

I would like the following numbers to be proportional so that 11, 
doesn't take up as much space as 17. See what I mean?    

\end{document}