Self defined widget styling

I am using Yuzo Related Posts on https://byte.nl/blog/ posts.
I had to create a core hack on yuzo-related-post/assets/functions/widget.php to get a custom widget style.

How can I apply my own widget style without a core hack on your plugin?
Can you add this option?

https://ww.wp.xz.cn/plugins/yuzo-related-post/