DroneOn, I did something like yours but instead of the 1x/Jx locations I just made plain 20x20 squares (posted on another thread as well), that way you can see the first layer coverage in each calibration location and hopefully be able to adjust the grid/mesh pattern better.
CalibrationTest.stl (71.4 KB) CalibrationTest_40300071.gcode (129.6 KB)