I use the same trick today! I have some "benchmark" macros set up which forcibly override the background color when I want to see where in the frame my operations are taking place.
> Didn't know there were people still trying to squeeze more out of that chipset nowadays.
You will be amazed. The demoscene has gotten insanely good since around 2017. Here are some of my favorites that all run on a stock Amiga 500 (with the trapdoor memory):
https://www.youtube.com/watch?v=2jciCr8zEhw
https://www.youtube.com/watch?v=iD9xk3SDSYc
https://www.youtube.com/watch?v=pYtleuGV7ok