scrlttr2: Increasing the headline space on the 2nd page

How can I increase the space between the headline and the following text on the second page of the scrlttr2 document?

\documentclass[ngerman,12pt]{scrlttr2}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[]{babel}
\usepackage[]{blindtext}

\setkomavar{fromname}{Max Mustermann}

\vbox to 50pt {\vfil
\hbox to 3cm{\rule{1cm}{1cm}}%
\vfil
}
}

\begin{document}
\begin{letter}{Unternehmen}
\opening{Sehr geehrte Damen und Herren,}

\blindtext[4]

\closing{Mit freundlichen Grüßen,}

\end{letter}
\end{document}


-

With the exception of the first page you can set the margins as usual. The first page works with pseudo length. The next pages use the standard settings provided by typearea.

To demonstrate this you can load the package showframe und manipulate length like \headsep. However I recommend the package geoemtry to influence the margins.

If I use the following settings in your example

\usepackage{showframe}