# How to change intensity of TikZ fading?

I am attempting to do a mirror/reflection effect using TikZ fadings, but the fade that I am currently able to achieve is too 'gentle' - the line fades, but all of the line remains. The line's reflection itself is in the correct position, but the intensity of the fade is not enough - I want the line to disappear quite quickly.

This is my MWE:

\documentclass[11pt,twoside]{book}

\usepackage{tikz}
\usepackage{afterpage}
\usepackage{xcolor}
\usepackage{geometry}

\geometry{
paperwidth=17.78cm,
paperheight=25.4cm,
marginparsep=6.35mm,
top=.5cm, % Top margin
bottom=1cm, % Bottom margin
left=2cm, % Left margin
right=2cm, % Right margin
}

\usepackage[
width=18.0975cm,
height=26.035cm,
center,
%cam,
%cross,
%frame
]{crop}

\begin{document}
\begin{titlepage}
\pagecolor{orange}\afterpage{\nopagecolor}

\begin{tikzpicture}
\draw[overlay, white, line width=1.1mm] (-3,-.35) .. controls (-2.5,-4.5) and (5,-3.5) .. (20,.5);
\begin{scope}[shift={(0,-6.15)},xscale=1,yscale=-1,rotate=360]
\draw[overlay, white, line width=1.1mm,path fading=south] (-3,-.35) .. controls (-2.5,-4.5) and (5,-3.5) .. (20,.5);  % Mirror Image
\end{scope}
\end{tikzpicture}
\end{titlepage}
\end{document}


Which produces this:

And this is the desired effect that I am trying to achieve:

Is it possible to achieve my desired effect using TikZ?

Thank you very much for any help in advance.

One can look up the definition of the original south fading in pgflibraryfadings.code.tex to find

\pgfdeclareverticalshading{pgf@lib@fade@south}{100bp}
{color(0bp)=(pgftransparent!100); color(25bp)=(pgftransparent!100);
color(75bp)=(pgftransparent!0); color(100bp)=(pgftransparent!0)}%



All I did was to change color(25bp)=(pgftransparent!100); to color(40bp)=(pgftransparent!100); in a fading I called South in

\documentclass[11pt,twoside]{book}

\usepackage{tikz}
\makeatletter
{color(0bp)=(pgftransparent!100); color(40bp)=(pgftransparent!100);
color(75bp)=(pgftransparent!0); color(100bp)=(pgftransparent!0)}%
\makeatother
\usepackage{afterpage}
\usepackage{xcolor}
\usepackage{geometry}

\geometry{
paperwidth=17.78cm,
paperheight=25.4cm,
marginparsep=6.35mm,
top=.5cm, % Top margin
bottom=1cm, % Bottom margin
left=2cm, % Left margin
right=2cm, % Right margin
}

\usepackage[
width=18.0975cm,
height=26.035cm,
center,
%cam,
%cross,
%frame
]{crop}

\begin{document}
\begin{titlepage}
\pagecolor{orange}\afterpage{\nopagecolor}

\begin{tikzpicture}
\draw[overlay, white, line width=1.1mm] (-3,-.35) .. controls (-2.5,-4.5) and (5,-3.5) .. (20,.5);
\begin{scope}[shift={(0,-6.15)},xscale=1,yscale=-1,rotate=360]

With 50bp instead of 40bp you get