Unfortunately, we cannot add a height parameter to JFBCFan. Facebook only exposes the width as a parameter and not the height. If they add height in the future, we'll be sure to include it, but until then it won't be possible.
In the meantime, I would suggest that you play around with the other parameters in the module. For example, turning off the stream, header, and showing less connections will get a substantially smaller size module. You can easily test out customizing the values using this Facebook page:
developers.facebook.com/docs/reference/plugins/like-box.