REQUIRES YOUTUBE CENTER - download it here https://github.com/YePpHa/YouTubeCenter/wiki/Developer-Version

It is NOT compatible with fullscreen. that feature is disabled.
It is NOT compatible with livestreams. disable the style during a livestream.

Instructions:

1 - open any video page

2 - make a screenshot

3 - measure the width of your player (use mspaint, NOT INSPECT ELEMENT)
3.1 - paste your screenshot to paint
3.2 - select the tool select
3.3 - select exactly the width of your video player
3.4 - ctrl + c
3.5 - resize paint canvas to a tiny rectangle
3.6 - ctrl + v
3.7 - look at the width of the canvas
you must be really precise, an error of 1 pixel will misplace the player
this value usually is 640, 853 or 1280 depending on your screen
DON'T use inspect element for this as it will change the size of the page

4 - enter that value in the box below

5 - after each install, disable, or enable, reload the page for it to be applied correctly