Firefix Reducing Youtube Video Player Size After Update To 113

So I recently upgraded to Firefox 113, and I really detest some of the changes in it. They changed a whole lot of UI things that really bug me, but the one I'm actively trying to fix is that if I have Firefox set up like a normal dang program, with the menu bar visible, it shrinks the YT video player by about 20% (which makes things super hard to see sometimes) and adds a ton of whitespace on the left and right sides of the page.

To get the video player the same size as I *previously had it before I upgraded*, I have to toggle off the menu bar - which means that a) there's no quick access to bookmarks or anything, and b) if I Alt to get to the menus, the size bounces up and down. What few relevant search results I've had point to a viewport size issue depending on whether the menu bar is enabled or not, but there's nothing on how to fix or change it.

I'm already using a CSS stylesheet to remedy *several* other annoyances, and I'm not averse to adding things to it, but I don't know enough to write it myself.

Anyone manage to tweak this?

 

...I'd edit the previous, but I can't seem to figure out how to.
Of course posting about it makes me try something new. Turning off the title bar also gets me the proper video player size back, leaving just the menu bar at the top of the screen. Bah. UI changes make me grumpy.

 

Try Firefox Nightly you might like it better.