I found my answer in the XtraCAD forum,

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The way I handle this is to only show mt text in paperspace. The text is still in model spec but only shows in paper space. see attached file with settings. I set my text up in the text styles to my desired print height ( 1/8", 3/32"). By going this route, it keeps my model space clean and I control all my text (size, alias, elevation) through my viewport when in paper space. Using this method, regardless of my viewport scale, my text will always  be the size I set it in my text styles.

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http://www.xtracad.com/forum/index.php?topic=10048.new#new

Neil