Efficiently Displaying a Paragraph in Trapezoidal Formation

Question

As part of an introduction to the contents of a book, I would like to display a particular paragraph in the formation of a trapezoid; and I suspect I will be able to do this (but rather laboriously) as follows:

\documentclass[12pt]{book}
\usepackage{scalefnt}
\usepackage{lipsum}
\begin{document}
\thispagestyle{empty}
\parshape 16 % A count of the number of lines.
0pt 0.73\linewidth
.015\textwidth \dimexpr0.70\textwidth
.03\textwidth \dimexpr0.67\textwidth
.045\textwidth \dimexpr0.64\textwidth
.06\textwidth \dimexpr0.61\textwidth
.075\textwidth \dimexpr0.58\textwidth
.09\textwidth \dimexpr0.55\textwidth
.105\textwidth \dimexpr0.52\textwidth
.12\textwidth \dimexpr0.49\textwidth
.135\textwidth \dimexpr0.46\textwidth
.15\textwidth \dimexpr0.43\textwidth
.165\textwidth \dimexpr0.40\textwidth
.18\textwidth \dimexpr0.37\textwidth
.195\textwidth \dimexpr0.34\textwidth
.21\textwidth \dimexpr0.31\textwidth
.225\textwidth \dimexpr0.28\textwidth
\hskip 95pt {\large{\scalefont{1.15}\textbf{A TITLE}}} \[8pt] \lipsum[4].
\end{document}

which produces

Now, in practice, I would like to produce an output more aesthetically pleasing. But it seems to me that in order to do so, the process involves some trial and error.

QUESTION: Is there a more efficient way of producing a trapezoidal paragraph than the way shown? Perhaps, some kind of a macro where one specifies the lengths of the two bases, or something of that sort---and which also will automatically center the last line?

Thank you.