Solved this! Zoom in and out on the map work as needed – the letter and numbers space.
I used to.Comp –
Created 3D nulls on the end of each grid line. Each null had a matching name to the letter / number it locks.
For example, to have the D stay locked to the grid line:
[thisComp.layer(“Null_D”).toComp([0,0,0])[0],45]