Define kerning in lualatex

Question

I am trying to define a kerning between V and /. (see question)

My approach is the following, but I don't see any differences between using the feature file and not using it.

\documentclass{standalone}
\usepackage{filecontents}

\begin{filecontents*}{mykern.fea}
languagesystem DFLT dflt;
languagesystem latn dflt;
feature kern {
pos \V  \SLASH -800;
} kern;

\end{filecontents*}

\usepackage{fontspec}
\setmainfont[FeatureFile=mykern.fea]{TeX Gyre Pagella}
%\setmainfont[]{TeX Gyre Pagella}
\usepackage{unicode-math}
\setmathfont[math-style=upright]{euler.otf}

\usepackage{microtype}
\usepackage{siunitx}

\begin{document}
\begin{tabular}{ll}
Text  & MV/m \\
equation & $MV/m$\\
two mathrm & $\mathrm{MV}/\mathrm{m}$\\
one mathrm & $\mathrm{MV/m}$\\
siunitx & \si[per-mode = symbol]{\mega\volt\per\metre}\\
%one mathrm & $\mathrm{MV/m}$\\
\end{tabular}
\end{document}

Answer 1

I made it changing the pos line to pos V \slash -100;.