Just looks like you forgot to add the grids to the higher tier mining vehicles.
Higher tier mining vehicles should have bigger grids IMO.
The basic miner is fine with the 8x2 grid, miner mk2 and mk3 should get the 10x2 grid, and miner mk4 and mk5 should get the 10x4 grid.

This translates to adding the following lines to data.lua in this mod:

data.raw["car"]["vehicle-miner-mk2"].equipment_grid = "bob-tank"
data.raw["car"]["vehicle-miner-mk3"].equipment_grid = "bob-tank"
data.raw["car"]["vehicle-miner-mk4"].equipment_grid = "bob-tank-2"
data.raw["car"]["vehicle-miner-mk5"].equipment_grid = "bob-tank-2"