[hercules21]

Alright, I've come up with a nice table for ascertaining the centering sub-grade that takes into account both directions on both the front and back.

<img width="300" src="http://i1285.photobucket.com/albums/a585/keisenhower/cards/cards_forum/grading_examples/centering_table_zps4071c350.jpg">

This table shows that in order to get a given grade in the far left column, the centering must meet the requirements listed in that row (for both front and back centering), using that ratio measured in the <b>worst</b> direction on that side.

Here is an example:
1) Measure the pixel sizes of the borders (both top/bottom and left/right) on the front.
2) Calculate the ratios in both directions, and normalize them to add up to 100. So a 33/22 ratio normalizes to 61/39.
2) Take the ratio for the direction that is the worst (furthest from 50/50) and round that ratio "down" to a multiple of 5, like is shown in the table. So 61/39 rounds down to a 60/40.
3) Find that ratio in the middle column and circle it. So in this case we circle both 60/40's which are next to the 8 and 8.5.
(At this point, you know the centering can't be any better than an 8.5)
4) Now, do the same thing (steps 1 and 2) on the back.
5) For the back, find that ratio in the far right column and circle it.
6) Finally, <b>whichever circle is the lowest in the table defines your final centering sub-grade</b>

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