Setting a custom font size for part of the document that frequently uses size-specific commands like \large and \huge

Question

For my thesis I'm using a popular template (MasterDoctoralThesis) that comes with a beautiful title page. I have to adhere to APA guidelines of 12 pt text and onehalf spacing, which are not the default settings for this template, and it stretches the content to almost 2 full pages.

Is there a way to make just this title page use 11 pt font and single spacing? Font size seems to have the largest impact, as using the singlespacing environment from the setspace package leads to little change. Changing the manually applied spaces in the code to make it all fit on one page makes everything look cramped, sadly. Using something like \fontsize{11pt}{13pt}\selectfont inside the center block had no effect.

The MWE below generates a mock-up page of how the design is supposed to look. You can simulate the problem by changing the font size to 12 pt and the singlespacing block to onehalfspacing.

\documentclass[11pt]{article}
\usepackage[
    paper=a4paper,
    inner=1in,
    outer=1in,
    bindingoffset=.5cm,
    top=1in,
    bottom=1in,
]{geometry}
\usepackage{setspace}
\usepackage{fontspec}
\setmainfont{Times New Roman}

\begin{document}
    \begin{singlespacing}
        \begin{center}
            \vspace*{.06\textheight}
            {\scshape\LARGE UNIVERSITY NAME\par}\vspace{1.5cm}
            \textsc{\Large THESIS TYPE}\\[0.5cm]
        
            \rule{.9\linewidth}{.6pt} \\ [0.4cm]
            {\huge \bfseries LONG\\ THESIS\\ TITLE\par}\vspace{0.4cm}
            \rule{.9\linewidth}{.6pt} \\[1.5cm]
        
            \begin{minipage}[t]{0.3\textwidth}
                \begin{flushleft} \large
                    \emph{Author:}\\
                    AUTHOR NAME
                \end{flushleft}
            \end{minipage}
            \begin{minipage}[t]{0.6\textwidth}
                \begin{flushright} \large
                    \emph{First supervisor:} \\
                    FIRST SUPERVISOR\\
                    INSTITUTE, CITY \\ \bigskip\bigskip
                    \emph{Second supervisor:} \\
                    SECOND SUPERVISOR\\
                    UNIVERSITY, CITY
                \end{flushright}
            \end{minipage}\\[3cm]
        
            \vfill
        
            \large \textit{A thesis submitted in fulfillment of the requirements\\ for the degree of DEGREE NAME}\\[0.3cm]
            \textit{in}\\[0.4cm]
            SUBJECT NAME\\[2cm]
        
            \vfill
        
            {\large \today}\\[4cm]
        
            \vfill
        \end{center}
    \end{singlespacing}
\end{document}

Answer 1

You can to change [11pt] to [12pt] then in that title page just reduce the fonts one step so change \huge to \LARGE, \LARGE to \Large and change \Large to \large, then adjust any explicit lengths such as \\[1.5cm] to whatever looks tight for your new design.