userChrome.css modification for Thunderbird Portable

I assume it is this file:

\ThunderbirdPortable\Data\profile\chrome\userChrome.css

I have been trying to mod this simply with

/* Change Browser Fonts */
* { font-size: 14pt !important;
font-family: tahoma !important; }

and there is no effect on my TB - any thoughts??

Is this the wrong file? wrong syntax???

Is there a chromedit that will mod TB Port userChrome

help?