[Tex/LaTex] Evenly spacing figures vertically across page

Question

I am compiling an appendix for my dissertation consisting only of figures. Currently the gap between the top figure and the top of the page is smaller than the gap between the lower figure and the bottom of the page. I want to place three figures on each page, with even vertical spacing. How would I adapt the following code to do this:

\begin{figure}
\centerline{
\begin{minipage}[c]{0.6\textwidth}
\centering
\includegraphics[width=\textwidth]{figs/DCP/pen1-1}
\end{minipage}
\hspace{0.5cm}
\begin{minipage}[c]{0.6\textwidth}
\centering
\includegraphics[width=\textwidth]{figs/DCP/cbr1-1} 
\end{minipage}
}
\caption[]{DCP test 1.1}
\label{graphs1-1}
\end{figure}

\begin{figure}
\centerline{
\begin{minipage}[c]{0.6\textwidth}
\centering
\includegraphics[width=\textwidth]{figs/DCP/pen1-2}
\end{minipage}
\hspace{0.5cm}
\begin{minipage}[c]{0.6\textwidth}
\centering
\includegraphics[width=\textwidth]{figs/DCP/cbr1-2}
\end{minipage}
}
\caption[]{DCP test 1.2}
\label{graphs1-2}
\end{figure}

\begin{figure}
\centerline{
\begin{minipage}[c]{0.6\textwidth}
\centering
\includegraphics[width=\textwidth]{figs/DCP/pen1-3}
\end{minipage}
\hspace{0.5cm}
\begin{minipage}[c]{0.6\textwidth}
\centering
\includegraphics[width=\textwidth]{figs/DCP/cbr1-3}
\end{minipage}
}
\caption[]{DCP test 1.3}
\label{graphs1-3}
\end{figure}

Note: each figure consists of two graphs side-by-side.

Answer 1

You definitely don't want the figure environment. Try

\documentclass{memoir}

\usepackage[demo]{graphicx}

\usepackage{showframe}

\makeatletter
\newenvironment{appfigure}
  {\par\vspace{\fill}\centering
   \begin{adjustwidth}{-.12\textwidth}{-.12\textwidth}%
   \def\@captype{figure}%
   \setkeys{Gin}{width=.6\textwidth}}
  {\end{adjustwidth}\par}
\makeatother

\begin{document}

\mainmatter

\appendix

\chapter{Appendix with figures}

\begin{appfigure}
\includegraphics{figs/DCP/pen1-1}\hfill
\includegraphics[]{figs/DCP/cbr1-1} 
\caption[]{DCP test 1.1}
\label{graphs1-1}
\end{appfigure}

\begin{appfigure}
\includegraphics{figs/DCP/pen1-1}\hfill
\includegraphics[]{figs/DCP/cbr1-1} 
\caption[]{DCP test 1.1}
\label{graphs1-2}
\end{appfigure}

\begin{appfigure}
\includegraphics{figs/DCP/pen1-1}\hfill
\includegraphics[]{figs/DCP/cbr1-1} 
\caption[]{DCP test 1.1}
\label{graphs1-3}
\end{appfigure}

\begin{appfigure}
\includegraphics{figs/DCP/pen1-1}\hfill
\includegraphics[]{figs/DCP/cbr1-1} 
\caption[]{DCP test 1.1}
\label{graphs1-4}
\end{appfigure}

\begin{appfigure}
\includegraphics{figs/DCP/pen1-1}\hfill
\includegraphics[]{figs/DCP/cbr1-1} 
\caption[]{DCP test 1.1}
\label{graphs1-5}
\end{appfigure}

\pagebreak

\begin{appfigure}
\includegraphics{figs/DCP/pen1-1}\hfill
\includegraphics[]{figs/DCP/cbr1-1} 
\caption[]{DCP test 1.1}
\label{graphs1-6}
\end{appfigure}

\begin{appfigure}
\includegraphics{figs/DCP/pen1-1}\hfill
\includegraphics[]{figs/DCP/cbr1-1} 
\caption[]{DCP test 1.1}
\label{graphs1-7}
\end{appfigure}

\begin{appfigure}
\includegraphics{figs/DCP/pen1-1}\hfill
\includegraphics[]{figs/DCP/cbr1-1} 
\caption[]{DCP test 1.1}
\label{graphs1-8}
\end{appfigure}

\end{document}