Customizing protrusion in microtype using \SetProtrusion

I am using microtype in a document (with pdftex) and I would like to alter the amount of protrusion that small numbers (i.e. the digits 0-9) are subject to.

However, I cannot make \SetProtrusion work even in the most basic case - this MWE produces no protrusion of 1 or 2:

\documentclass{article}
\usepackage{microtype}
\SetProtrusion
{encoding = *}
{1= {1000,1000}, {2=1000,1000}}

\begin{document}

Lorem Ipsum ...
1\\
2\\
3\\
4\\
\end{document}


Following along the lines ofthis question I also tried to ensure that my settings are read last, hopefully overriding the defaults (from mt-cmr.cfg)

 \usepackage{microtype}
\SetProtrusion
{encoding = *}
{1= {1000,1000}, {2=1000,1000}}

\begin{document}

Lorem Ipsum ...
1\\
2\\
3\\
4\\\documentclass{article}

\end{document}


However this does not work either.

The only way I was able to affect the protrusion was by replacing the default protrusion list wholesale, as in

\usepackage{microtype}
\SetProtrusion
[name=cmr-default]
{encoding = *}
{1= {1000,1000}, {2=1000,1000}}

\begin{document}

Lorem Ipsum ...
1\\
2\\
3\\
4\\\documentclass{article}

\end{document}


But this means that all the defaults settings for glyphs I have not modified are gone.

What is the correct way to modify protrusion for certain character/size combinations while maintaining all the default settings for everything else ?

-

The following works as intended, protruding only the small 1 and 2, and maintaining the protrusion rules that are set in mt-cmr.cfg (shown here with + and - as these characters are the most protruded in those sets).

\documentclass{article}
\usepackage{microtype}
\SetProtrusion
{ encoding = OT1,
family = cmr,
size = -small }
{ 1 = {1000,1000},
2 = {1000,1000} }

\begin{document}

Lorem Ipsum ... \\
1\\
2\\
-\\
+\\
\\
\scriptsize{1}\\
\scriptsize{2}\\
\scriptsize{+}\\
\scriptsize{-}\\

\end{document}


I believe the problem lies in the use of {encoding = *} - * is not a wildcard character as far as microtype is concerned, but rather something that expands to a default value (section 4 of the manual).

-