How to determine centering on cards with irregular borders

ringer

Hi all, I’m trying to figure out how to measure cards centering when the frame or border is not regular. Take a look at these two cards. You can see hell the angular water makes it difficult to know how to determine such rain. On the other one do you use the border of the picture or is the name underneath somehow included? Any suggestions?

NGS428

For the 91 Donruss R/L is easy, for the T/B I would go from the top white border and compare that to the space of the area below the red bar with Ken’s name on it. This one is centered to the bottom right, not worth grading if you are wondering.

The 90 UD, L/R is easy, T/B I would use the area on top of the “OF” compared to the bottom of the picture just over Ken’s name. This one is centered a bit high, but L/R is good. I see a bunch of what may be dust and a mark of some type on the card. Not sure if any of that is on the card.

Here is a centering calculator I created for measuring images of cards.

https://drive.google.com/file/d/1gvoWEKuCaUZf3KmyniGd3LRWIL3Pq4zw/view?usp=drivesdk

ringer

Thank you.