Indenting with poemscol package

I'm trying to typeset a poem collection with poemscol. The result looks like this:

I'd like to control the distances marked in red (I don't want any moving to the right); but all attempts with \setlength of \leftmargin, \titleindentamount etc. don't work, and I've never ventured this far into page setup details. Can someone provide a hint how this usually works?

The current code:

\documentclass[9pt, a5paper]{scrbook}
\usepackage[a5paper]{geometry}
\usepackage{fancyhdr}
\usepackage{poemscol}
\begin{document}
\poemtitle{I dwell in Possibility}
\begin{poem}
\begin{stanza}
\textsc{I dwell} in Possibility --\\
A fairer House than Prose --
\end{stanza}
\end{poem}
\end{document}


I tried to track the indentation in the poemscol package, but without success. I cannot find the commands in the package that control this behavior. What is their name and where are they?

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Welcome to TeX.SX! You can insert pictures: use the normal way (clicking on the "screen" icon) and then remove the ! before the reference to the picture. A user with enough reputation will reinstate the !. –  egreg Nov 10 '12 at 11:03
Welcome to TeX.sx! Please add a minimal working example (MWE) that illustrates your problem. It is considered a lot better to put in some code that will compile, as it makes it a lot easier for us to copy it into our text editor and work with it, and see exactly what it is you are trying to do. –  henrique Nov 10 '12 at 11:14
I'm afraid that poemscol is rather rigid in its settings; the indentations are hard coded in the environments and not expressed by changeable parameters. –  egreg Nov 10 '12 at 13:07

The indentation of the poem author is indeed, as egreg has commented, hardcoded in the epigraphquote environment, so you have to change its definition. The environment used to typeset the poem proper is pmclverse (which inherits an optional argument from the poem environment). Its formula to determine margins only seems to allow to increase, but not to decrease the left margin, so I decided to change (simplify) its definition as well.

\documentclass[9pt, a5paper]{scrbook}
\usepackage[a5paper]{geometry}
\usepackage{fancyhdr}
\usepackage{poemscol}
\renewenvironment{epigraphquote}%
{\list{}{%
\topsep 0pt%
\partopsep 0pt%
\listparindent 0pt%
\leftmargin  1em% original value: 1.5em
\rightmargin 1em% original value: 1.5em
}%
\item\relax}
{\endlist}
\makeatletter
\renewenvironment{pmclverse}[1][]{%
\let\\=\@centercr%
\list{}{%
\itemsep\z@
\itemindent -\runoverindentvalue
\listparindent \itemindent
\leftmargin 2em% change as desired
\rightmargin 2em% change as desired
}%
\item[]}
{\endlist}
\makeatother
\begin{document}
\poemtitle{I dwell in Possibility}