Modify font size when using FncyChap package

The latex package FncyChap provides several nice pre-defined style for chapter headings. However, I found out the chapter title takes too much space sometimes; it may take more than two thirds of the page. Thus, it is necessary to reduce the font size for the chapter title.
The first step is to find out what is the default value in the pre-defined layout, which can be found in the FncyChap document. Take the ‘Lenny ’ style as an example. The default settings for the chapter title is

\ChTitleVar{\Huge\bfseries\rm}

To change the title size from ‘\Huge’ to other values, in the preamble, add the following

\makeatletter

\ChTitleVar{\huge\bfseries\rm}

\makeatother

Now the font size is smaller and suitable for long chapter titles.