Modification of the Chat window...includes a bigger font for your chatbar
If you have a customized eq2ui_fonts.xml already, simply add the line 
<TextStyle Algorithm="Simple" FontName="Arial" Language="english" Name="Font_ChatInput2" PointSize="18" UseCachedFont="true"/>
to the file you already have blow the first line (<Namespace Name="Fonts">)

To install :

Exit the game.

Unzip.

Copy the files to your personal EQ2 UI directory (eg c:\Program Files\Sony\Everquest II\UI\MyMods\)

Make a file "EQ2.INI" in the Everquest II folder (eg c:\Program Files\Sony\Everquest II\)
Edit the file with the following text - changing your personal UI folder name where applicable:
cl_ui_skinname MyMods
cl_ui_subdir UI/

Restart the game and have fun ;)