\documentclass{beamer}
\def\rmdefault{lcmss} % no roman
\def\sfdefault{lcmss}
\def\ttdefault{lcmtt}
\def\itdefault{sl}
\def\sldefault{sl}
\def\bfdefault{bx}
\makeatletter
\def\itwentypt{19.907}
\def\@setfontsize@parms#1#2#3#4#5#6#7#8{%
\lineskip #1\relax%
\parskip #2\relax
\abovedisplayskip #3\relax
\belowdisplayskip #4\relax
\abovedisplayshortskip #5\relax
\belowdisplayshortskip #6\relax
\setbox\strutbox=\hbox{\vrule \@height#7\p@\@depth#8\p@\@width\z@}%
\baselineskip\baselinestretch\baselineskip