Chapter number in `Lenny` and roman numerals to Old Style

Question

Is there a way to change the chapter number in fncychap as well as the roman numerals in the \frontmatter to be old style figure style?

\documentclass{amsbook}
\usepackage[osf]{mathpazo}
\usepackage[Lenny]{fncychap}
\ChRuleWidth{1.618pt}
\ChTitleVar{\raggedright  \huge }
\ChNameVar{\raggedleft  \Huge }

\begin{document}
\frontmatter 
\tableofcontents
\chapter{One}
Hi
\newpage
\chapter{Two}
Hi
\mainmatter
\chapter{Three}
Hi
 \end{document}

Answer 1

This seems to be working quite nicely (at least for the chapter numbering). The only problem that I see is one of alignment.

\documentclass{amsbook}
\usepackage[osf]{mathpazo}
\usepackage[Lenny]{fncychap}
\ChRuleWidth{0pt} %0.618pt for Lenny
\ChNameVar{  \Huge \bfseries  }  
\ChNumVar{\fontsize{45}{100} \rm}
\ChTitleVar{  \huge }

\begin{document}
\frontmatter 
\tableofcontents
\chapter{This is Chapter 1}
\section{Section 1, Chapter 1}
Hi
\newpage
\chapter{This is Chapter 2}
\section{Section 1, Chapter 2}
Hi
\mainmatter
\chapter{This is Chapter 3}
\section{Section 1, Chapter 3}
Hi
\end{document}