Prova questo codice (è preso dal file beamerbasenotes.sty, con qualche modifica, in rosso); vedi se può andar bene. Ammetto che non ho capito del tutto come beamer imposta la pagina per le note. I valori che ho messo sono il semplice frutto di tentativi:?
`\makeatletter
\renewcommand\beamer@outsideframenote[2][]{%
\beamer@savemode%
\ifbeamer@inlecture%
\def\beamer@noteenvstart{}%
\def\beamer@noteenvend{}%
\setkeys{beamernotes}{#1}%
\ifbeamer@notes
\begingroup
\setbeamertemplate{itemize item}{\textbullet}
\setbeamertemplate{itemize subitem}{–}
\setbeamertemplate{enumerate item}{\insertenumlabel.}
\setbeamertemplate{enumerate subitem}{\insertenumlabel.\insertsubenumlabel}
\def\@oddhead{}
\def\@oddfoot{}
\let\@evenhead\@oddhead
\let\@evenfoot\@oddfoot
\def\beamer@backgroundtemplate{}%
\setbeamercolor{item}{fg=black,bg=white}
\color{black}%
\nointerlineskip
\hbox{\hskip-0.8cm\hskip1cm\vbox to\textheight{%
%pretend to have “standard'' margins
\edef\beamer@origlmargin{\Gm@lmargin}%
\edef\beamer@origrmargin{\Gm@rmargin}%
\def\Gm@lmargin{0.58cm}%
\def\Gm@rmargin{1cm}%
\textwidth=10.8cm%
\hsize=\textwidth%
\vskip-\headheight%
\def\insertnote{\vbox{}%
\beamer@noteenvstart#2\beamer@noteenvend%
}%
\usebeamertemplate*{note page}%
\vfil%
\vskip-4pt% foot separator
\vskip-\footheight}\hskip-\Gm@lmargin\hskip1cm}%
\ifbeamer@twoscreensnotes%
\pgfpagescurrentpagewillbelogicalpage{2}%
\advance\c@page by-1\relax%
\fi%
\clearpage
\endgroup
\fi%
\fi%
\beamer@resumemode}
\makeatother`
Ciao
Ivan