f0tz!baerchen's pixel script has the option of changing event sizes.
I'm not sure what script that is, but I suggest using f0tz!' script. (I'm using it now that I know more about it)
For his script you just add a comment to the first line of the event that says
event_size: (width in pixels),(height in pixels)
EDIT: Ok having rechecked, it is his script... anyway... that's the syntax.
here is my character size (I made mine a bit larger than the default I think)