Custom CSS for BasicUI

Hi, when I run BasicUI on my phone, it takes up way too much space. In CSS this can be fixed very easily. I made changes using chrome inspect element feature, and got the modified “smarthome.css” file. But, can not get it to be used. I located this css file in the “org.eclipse.smarthome.ui.basic-0.9.0.b2.jar” file. If I replace the css file located in this jar file, it still does not use the new css.

Is there any simple way to create a custom css file for BasicUI?