Some fixes for Youtube polymer engine
< Youtube polymer engine fixesについてのフィードバック
Redirecting from short does not always work, this script works clearly - FuckYTShorts - Source code
I checked in the trends, your script did not redirect two short ones, and the other script worked for everyone.
Regarding custom thumbnail sizes -- I will look into it. About shorts -- script you linked does the job reloading page, which I try to avoid in my script for multiple reasons.
Add intermediate thumbnail sizes, between 180 and 240, or enter a custom value.
If you about setting for main page, then select "manual" and enter value you want (in pixels).
For search page there is no 180 option.
Updated shorts-related code (there were some bugs).
Add intermediate thumbnail sizes, between 180 and 240, or enter a custom value.