Mining/Dumping Designations

Please add an option to do half a tile designation
Full
1 2 3 4
1 - - - -
2 - - - -
3 - - - -
4 - - - -
Half
1 2 3 4
1 - - - -
2 - - - -
3
4

It would be great if there was an option to control the designations on the smallest grid unit level (1x1), instead of 4x4. And then there could be a way to choose the designator tool size 1x1, 2x2 or 4x4.
Then I could have those nice, smooth, landfilled shorelines, instead of minecraft grid world I'm creating now.