This latest version of m10-template includes a modification to corners. The larger space that exists between PCB and the frame leaves room to pass up to 5X 1mm wires for inter M10CUBE connection like carrying high speed LVDS RS485 connection between I/O modules and CPU, or getting PSU values to other PCB for monitoring. In general all 4 corners can accommodate extra wiring for passing through to other PCBs in the M10CUBE space for signals that not met by the 40 pin RASPI connector. Since has no cost It will be an option for someone to use.
Big holes 1,2,3,4 are 3.3 mm in diameter. That is for the pass through 3mm threaded rod to mechanical stabilize the frames.
small holes are for mounting the PCB on the frame
PCB dimension remains the same 91X91 mm