Show miniframes with split outer themes

This seems to be working as I indended. It's a bit hackish, and it only works with the compress option.

\documentclass[compress,aspectratio=43]{beamer}

\useoutertheme{miniframes}
\useoutertheme{split}
\usecolortheme{whale}

% For convenience, move this to a style or theme file
\makeatletter

\newcount\beamer@xoff
\newcount\beamer@prev@section
\newcount\beamer@prev@miniframes
\beamer@xoff=0
\beamer@prev@section=0
\beamer@prev@miniframes=0

\def\insertsubsectionnavigationhorizontalminiframes#1#2#3{%
  \hbox to #1{{%
    \usebeamerfont{subsection in head/foot}\usebeamercolor[fg]{subsection in head/foot}%
    \beamer@currentsubsection=0%
    \def\sectionentry##1##2##3##4##5{}%
    \def\slideentry##1##2##3##4##5##6{%
      \ifnum##1>\beamer@prev@section%
        \beamer@xoff=##3\relax%
        \beamer@prev@miniframes=0\relax%
      \fi
      \ifnum##6=\c@part\ifnum##1=\c@section%
      \ifnum##2>\beamer@currentsubsection%
      \beamer@xoff=0\relax%
      \beamer@currentsubsection=##2%
      \box\beamer@sectionbox\hskip1.875ex plus1fill%
      \ifnum\beamer@prev@miniframes>0\relax%
        \beamer@tempdim=\beamer@boxsize%
        \multiply\beamer@tempdim by \beamer@prev@miniframes%
        \advance\beamer@tempdim by -\beamer@boxsize%
        \advance\beamer@tempdim by 2pt%
        \ifnum##2>1%
          \advance\beamer@tempdim by 1.875ex%
        \else
          \advance\beamer@tempdim by -\beamer@boxsize%
        \fi
      \else
        \beamer@tempdim=0pt%
      \fi
      \setbox\beamer@sectionbox=
      \hbox{\def\insertsubsectionhead{\kern\beamer@tempdim##5}%
         \def\insertsectionheadnumber{##1}%
         \def\insertsubsectionheadnumber{##2}%
         \def\insertpartheadnumber{##6}%
         \ifnum\c@subsection=##2%
        \beamer@link(##4){{\usebeamertemplate{subsection in head/foot}}}\else%
        \beamer@link(##4){{\usebeamertemplate{subsection in head/foot shaded}}}\fi}%
      \ht\beamer@sectionbox=1.875ex%
      \dp\beamer@sectionbox=0.75ex%
      \else%
      \beamer@prev@miniframes=##3%
      \fi%
      \setbox0=\hbox{\insertsectionhead\unskip}\ifdim\wd0>0pt\ifnum##3>0%
      \beamer@xpos=##3\relax%
      \advance\beamer@xpos by -\beamer@xoff%
      \hbox to 0pt{%
        \beamer@tempdim=0.5pt%
        \raise\beamer@tempdim\hbox{%
          \ifnum##2>0%
            \beamer@tempdim=\beamer@boxsize%
            \multiply\beamer@tempdim by\beamer@xpos%
            \advance\beamer@tempdim by -\beamer@boxsize%
            \advance\beamer@tempdim by 2pt%
            \advance\beamer@tempdim by \wd\beamer@sectionbox%
          \else%
            \beamer@tempdim=\beamer@boxsize%
            \multiply\beamer@tempdim by\beamer@xpos%
            \advance\beamer@tempdim by 1.875ex%
          \fi%
          \kern\beamer@tempdim\hbox{\beamer@link(##4){%
              \usebeamerfont{mini frame}%
              \ifnum\c@section=##1%
                \ifnum\c@subsection=##2%
                  \usebeamercolor[fg]{mini frame}%
                  \ifnum\c@subsectionslide=##3%
                    \usebeamertemplate{mini frame}%
                  \else%
                    \usebeamertemplate{mini frame in current subsection}%
                  \fi%
                \else%
                  \usebeamercolor{mini frame}%
                  \usebeamertemplate{mini frame in other subsection}%
                \fi%
              \else%
                \usebeamercolor{mini frame}%
                \usebeamertemplate{mini frame in other subsection}%
              \fi%
            }}}\hskip-10cm plus 1fil%
          }\fi\fi%
      \else%
      \fakeslideentry{##1}{##2}{##3}{##4}{##5}{##6}%
      \fi\fi%
      \beamer@prev@section=##1%
      \ignorespaces}%
    #2\hskip.3cm\setbox\beamer@sectionbox=\hbox{}%
    \hskip-1.875ex plus-1fill\dohead%
    \box\beamer@sectionbox\hfil\hskip.3cm%
    #3}}}

\setbeamercolor{mini frame}{parent=subsection in head/foot}

\ifbeamer@compress

\defbeamertemplate*{headline}{split theme miniframes}
{%
  \leavevmode%
  \begin{beamercolorbox}[wd=.5\paperwidth,ht=2.5ex,dp=1.125ex]{section in head/foot}%
    \insertsectionnavigationhorizontal{.5\paperwidth}{\hskip0pt plus1filll}{}%
  \end{beamercolorbox}%
  \begin{beamercolorbox}[wd=.5\paperwidth,ht=2.5ex,dp=1.125ex]{subsection in head/foot}%
    \insertsubsectionnavigationhorizontalminiframes{.5\paperwidth}{}{\hskip0pt plus1filll}%
  \end{beamercolorbox}%
}

\else

\defbeamertemplatealias{headline}{split theme miniframes}{split theme}
\setbeamertemplate{headline}[split theme miniframes]

\fi

\makeatother

% This is to enable the feature
\setbeamertemplate{headline}[split theme miniframes]

\begin{document}
\frame{\titlepage}
\frame{\tableofcontents} % no miniframes in the front matter (good)
\section{First Section}
\frame{} \frame{} \frame{} % miniframes without subsections (good)
\section{Second Section}
\subsection{Subsection 1}
\frame{} \frame{}
\subsection{Subsection 2}
\frame{} \frame{} \frame{}
\section{Third Section} % correct miniframes with mixed sections/subsections
\frame{} \frame{} \frame{}
\subsection{Subsection 3}
\frame{} \frame{} \frame{}
\section*{} % no miniframes in back matter (good)
\frame{End}
\end{document}