fontsize with ttf font ?

[M.B. Schiekel]

Hi LyX-friends,

in my LaTeX-Preamble in LyX:
\usepackage{fontspec}
\setmainfont{arial.ttf}

and in the LyX-text in a TeX-Box
{\fontsize{5cm}{5.5cm} Really big text!}

and then PDF with LuaTeX
and then my "Really big text!" has not changed.
What's missing?

Thank you very much,
bernhard

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M.B. Schiekel,
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