Have tikz bezier control points defined off of page

Question

I have taken it on myself to reproduce some of my university's PPT templates (not that I necessarily love the design, but I have some good reasons for undertaking this venture) using Beamer. I have taken the below image of one of the templates and, using bezier curves, converted it into Tikz code.

The result looks pretty good to me, the only problem is, when defining the control points which describe the curves in the picture, some of the point lay off of the screen (i.e. they are negative values), which lowers the bottom edge of the bounding box of the Tikz image, and has the effect of "shifting up" the whole image (the largest negative value lay at the bottom edge of the page, shifting 'y=0' up by some amount). Essentially, the thing that solved this poster's problem is what is causing mine.

Is there any way to allow either the control points to exist outside of the bounding box or let the edge of the box "slide" off the page? Or maybe some other solution that I'm not thinking of? I am fairly practiced with LaTeX in general, but not so much with Tikz or Beamer specifically. I'm not sure if the solution will be Beamer- or Tikz-specific, but this seems very much like a Tikz thing to me. If there is another way to define the curves, I would be open to learning new things, but drawing beziers with control points is so dead-simple that I would hate to leave this method.

MWE:

beamerthemeMWE.sty:

\RequirePackage{tikz}
\RequirePackage{mwe}

\definecolor{CincinnatiRed}{RGB}{224,1,34}

\newcommand{\footerheight}{2}

\setbeamertemplate{navigation symbols}{}

\setbeamertemplate{footline}{
  \leavevmode\hbox{%
    \begin{tikzpicture}
        %red swoopy bit
        \path[fill=CincinnatiRed] (\paperwidth,\footerheight) .. controls %
        (0.898*\paperwidth,0.752*\footerheight) and (0.557*\paperwidth,-0.381*\footerheight) .. %
        (0,0.548*\footerheight) -- (0,0.957*\footerheight) .. controls %
        (0.529*\paperwidth,-0.169*\footerheight) and (0.882*\paperwidth,0.723*\footerheight) .. (\paperwidth,\footerheight); %
        %black swoopy bit
        \path[fill=black] (0,0) -- (\paperwidth,0) -- (\paperwidth,\footerheight) .. controls %
        (0.898*\paperwidth,0.752*\footerheight) and (0.557*\paperwidth,-0.381*\footerheight) .. %
        (0,0.548*\footerheight) -- cycle; %
        %white line
        \draw[white] (\paperwidth,\footerheight) .. controls (0.872*\paperwidth,0.647*\footerheight) and %
        (0.555*\paperwidth,-0.228*\footerheight) .. (0,0.148*\footerheight); %
        %university logo
        \node[anchor=south east,inner sep=0pt](UC_logo) at %
        (0.966*\paperwidth,0.129*\footerheight){\includegraphics[scale=0.09] %
        {example-image-a}};
    \end{tikzpicture}
}}

mwe.tex:

\documentclass[aspectratio=169]{beamer}
\usetheme[]{MWE}

\begin{document}
\begin{frame}
\end{frame}
\end{document}