I have drawn a figure (figure 3 in the current version, which I drew largely with Google SketchUp) showing the exact dimensions of the readout cells. Please feel free to insert those into the BCAL specification in the MC.
(There was some discussion today about revisiting the segmentation for the outer layers, but that will be done at a later date; for now, we are holding to the 6x4 for inner and 2x2 for outer).