How to Change Bottom Margins on Specific Page Style?

Question

I'm using fancyhdr. My fancy page style has no footer (only footnotes). However, on chapter titles, I am using a plain pagestyle, which has the footnote on the bottom. In any case, I would like to be able to have different bottom margins on each of these page styles - 0.25in for the plain pagestyle, and 0.15in for the fancy page style. How do you accomplish this?

\documentclass{book}
\usepackage{fancyhdr}
\usepackage[includeheadfoot,top=0.25in,bottom=0.1in,left=0.75in,right=0.4in,paperwidth=6in,paperheight=9in]{geometry}
\usepackage{blindtext}

\fancyhf{}
\fancyhead[RE,RO]{Right}
\fancyhead[LE,LO]{Left}

\begin{document}

\chapter{My Chapter}

\blindtext[3]

\blindtext[3]

\blindtext[3]

\blindtext[3]

\end{document}

Answer 1

Just for fun. You could also use table, or create a new float type. It really doesn't matter unless you want to add another bottom float to the page. Without a caption, it won't show up on the list of figures.

\documentclass{book}
\usepackage{fancyhdr}
\usepackage[includeheadfoot,top=0.25in,bottom=0.1in,left=0.75in,right=0.4in,paperwidth=6in,paperheight=9in]{geometry}
\usepackage{blindtext}

\fancyhf{}
\fancyhead[RE,RO]{Right}
\fancyhead[LE,LO]{Left}

\fancypagestyle{plain}{\fancyhf{}}% plain=empty

%\makeatletter
%\let\ps@plain=\ps@empty
%\makeatother

\newcommand{\addpageno}{\begin{figure}[b]
\makebox[\textwidth]{\thepage}
\end{figure}}

\begin{document}

\chapter{My Chapter}
\addpageno

\blindtext[3]

\blindtext[3]

\blindtext[3]

\blindtext[3]

\end{document}