Reducing/removing gap between header and custom chapter title

Question

I'm writing a portfolio/report with pdflatex and while trying to get a header and footer I have got a situation where there's now a significant gap between the header and the chapter title, whereas there's no gap on any of the other pages.

The code I'm using to style the headers, footers and titles is:

% Header/Footer 
\fancypagestyle{plain}{
  \fancyhf{}
  \fancyhead[L]{Name \texttt{<email@address>}}
  \fancyhead[R]{\leftmark}
  \fancyfoot[L]{Subject Name}
  \fancyfoot[R]{\thepage}
  \setlength{\headheight}{15.2pt}
  \setlength{\headsep}{6pt}
  \renewcommand{\headrulewidth}{0.4pt}
  \renewcommand{\footrulewidth}{0.4pt}
}

% Chapter Title formatting

\titleformat{\chapter}[display]
  {\normalfont\Huge \scshape}{\titlerule}{-28pt}{\thechapter\ \ \Huge}[\vspace{-2pt}\titlerule]
\titleformat{name=\chapter,numberless}[display]
  {\normalfont\Huge \scshape}{\titlerule}{-28pt}{\Huge}[\vspace{-2pt}\titlerule]
\titlespacing*{\chapter}{0pt}{50pt}{*2}
\begin{document}

% Article top matter ...
\maketitle

\pagestyle{plain}
\renewcommand{\chaptermark}[1]{\markboth{\thechapter.\ #1}{}}

Answer 1

Reduce the spacing using the second mandatory argument of \titlespacing (currently you are declaring a spacing of 50pt); a complete example setting the second argument to 0pt (notice that reducing this space too much might not be desirable since the rule from the header and the one from the chapter heading might get too close):

\documentclass{report}
\usepackage{fancyhdr}
\usepackage{titlesec}
\usepackage{lipsum}

% Header/Footer 
\fancypagestyle{plain}{
  \fancyhf{}
  \fancyhead[L]{Name \texttt{<email@address>}}
  \fancyhead[R]{\leftmark}
  \fancyfoot[L]{Subject Name}
  \fancyfoot[R]{\thepage}
  \setlength{\headheight}{15.2pt}
  \setlength{\headsep}{6pt}
  \renewcommand{\headrulewidth}{0.4pt}
  \renewcommand{\footrulewidth}{0.4pt}
}

% Chapter Title formatting

\titleformat{\chapter}[display]
  {\normalfont\Huge \scshape}{\titlerule}{-28pt}{\thechapter\ \ \Huge}[\vspace{-2pt}\titlerule]
\titleformat{name=\chapter,numberless}[display]
  {\normalfont\Huge \scshape}{\titlerule}{-28pt}{\Huge}[\vspace{-2pt}\titlerule]
\titlespacing*{\chapter}{0pt}{0pt}{*2}

\pagestyle{plain}
\renewcommand{\chaptermark}[1]{\markboth{\thechapter.\ #1}{}}

\begin{document}

\chapter{Test Chapter}
\lipsum[1-30]

\end{document}