Letterspacing, Minion Pro, and Tufte-LaTeX (problem with running header)

The Tufte-LaTeX classes define two commands that set up the spacing for \allcaps and \smallcaps. These commands are called \allcapsspacing and \smallcapsspacing. (I'm not terribly creative, I admit.)

You can define these commands to use the letterspacing feature provided by the fontspec package. Here's a complete example. Feel free to adjust the spacing to suit your typeface.

\documentclass{tufte-handout}

\usepackage{fontspec}
\setmainfont{Linux Libertine O}% or Minion Pro or what have you

% Set up the spacing using fontspec features
\renewcommand\allcapsspacing[1]{{\addfontfeature{LetterSpace=15}#1}}
\renewcommand\smallcapsspacing[1]{{\addfontfeature{LetterSpace=10}#1}}

\begin{document}

NATIVE ALL CAPS WITHOUT SPACING

\allcaps{ALL CAPS WITH SPACING}

{\scshape Native small caps without spacing}

\smallcaps{Small caps with spacing}

\end{document}