not sure about how to change the size of the message. But i would suggest that you put -> seta ch_recordMessage "0"
So you dont have to be annoyed by it at all :)

ch_recordMessage "0"
thanks, i know this command,
but i just want it to be smaller,
i know it can be done, but i dont remember what's the name of the command

I'm not sure but I think you can make it smaller with superhud.
Here's a nice superhud editor:
http://sourceforge.net/projects/superhudeditor/

You cannot make it smaller. Just disable it.