Lower the grid a few kilometers

The X quadrant of coverage is the top candidate for removal, in a good example of how minor tweaks can lead to big gains.

Limits and adjustments

By shifting the grid downwards, we would leave out one end of the C quadrant:

The limit for the maneuver (shifting) is a little more than \~10 km.

Conclusion:

We can eliminate X quadrant, shifting ~1 km.
We must to check the T quadrant, if it is possible to shift more, something from ~10 km to ~20 km.
The Y quadrant will remain.

We can assume that the limit is 15 km on C quadrant:

Checked

The T quadrant, and the \~20 km of "leak": seems that will be not possible to remove this quadrant,

Notes

At Y quadrant, \~30 km of "leak":

Click the image to check the values (must round to the integer part). The red box shows the general limits — from which we can also calculate the height and width.

Right and left sides:

at right side the quadrants 5 and 8 are tight, but the sea has no address to be represented by the grid-cells, and no "political border conflict".
at left side, the S quadrant has a good distance-gap, \~30 km.

osm-codes / CO_new